30x165mm Cartridges

The Soviet 30x165mm caliber is a family of high performance 30mm ammunition used in a wide variety of autocannons intended for aircraft, ships and ground vehicles. The range of 30x165mm caliber ammunition made for the ground forces was initially derived from the naval 30x165mm caliber used in the AO-18 six-barreled Gatling gun, but modified with a percussion primer instead of an electric primer. This rendered the ammunition non-interchangeable with the cartridges used by the navy and air force. Designated under the A43 index, the propellant consists of 6/7P-5BPfl double base stick powder. The same propellant is used in all 30x165mm cartridges covered in this article.

Ballistically, 30x165mm rounds are in the same class as NATO standard 30x173mm ammunition. According to the specifications, 30x165mm cartridges operate at a closely comparable pressure. The muzzle energy of 30x165mm rounds fired from a standard 2,416mm barrel (2A42, 2A72) is also closely comparable to equivalent 30x173mm ammunition. The original Soviet family of standard full-charge 30x165mm rounds for the ground forces, including HE-I and AP-T, were specified to develop an average maximum pressure of 3,600 kg.f/sq.cm or 353 MPa at a propellant temperature of 15°C. This is sometimes rounded down to 350 MPa in Russian literature. This is considered the normal operating pressure at a standard propellant temperature. For comparison, standard 30x173mm ammunition develops a maximum pressure of 345-360 MPa at "ambient" propellant temperature (21°C). The pressure curve and thus, work done by the propellant is generally quite similar, as double base stick powder is the most common choice of propellant for autocannons.

HEFI (OFZ)

3UOF8

OF47

 

3UOF8 is a high-explosive incendiary round intended for the destruction and neutralization of enemy combatants, helicopters, soft-skinned vehicles and light fortifications. The true classification of 3UOF8, corresponding to its designation of "OFZ" (Осколочно-фугасный Зажигательные), is HE-Frag-Incendiary, which can be abbreviated as HEFI. The HE-Frag effect is produced by the variable fuzing delays provided by the A-670M fuze, which has a fixed fuzing mode but differing behaviour on different targets and impact obliquities. In some cases, these shells may prove to be a potent alternative to 30mm armour-piercing shells against heavily armoured targets since they are able to effectively able to damage and destroy sighting systems and other important components including periscopes, machine guns and fuel tanks. The design of the OF47 projectile can be considered as the approximate equivalent of a scaled-up version of the 23mm OFZ (HEFI) projectile of the 23x152mm 3UOF5 round for the ZU-23-2 and ZSU-23-4. 

The A-670M nose fuze is used with the OF47 shell. According to Soviet manuals, the fuze provides self-destruction within 7.5 to 14.5 seconds after the shell leaves the muzzle, equivalent to a firing distance of 3,900 to 5,300 meters. However, on the websites of various manufacturers, the self-destruction time is listed as 9 to 14 seconds, equivalent to a firing distance of no less than 4,000 meters, as the flight time of the shell out to a range of 4,000 meters is almost exactly 9 seconds. It is possible that the built-in delay was increased on A-670M fuzes built by manufacturers outside the USSR. The self-destruction mechanism is pyrotechnic.

The A-670M fuze intrudes 30mm into the shell body and protrudes 39mm outside it. The fuze weighs 49 grams. Its body is made from cast steel. The fuze is armed by centrifugal forces and a pyrotechnic mechanism from 20 m to 100 m away from the muzzle, with 100 meters being the minimum safe distance. The fuze is of the superquick type, and has a graze-sensitive design. Its basic design follows that of earlier Soviet autocannon fuzes.

The fuze is percussion-actuated, and relies on free-floating steel balls for impact sensing. The nose of the fuze features a steel spike, which provides some penetration capability on lightly armoured targets, and serves as a secondary impact sensing mechanism. A steel tip is pressed into the hollow nose of the spike, securing the aluminium ballistic cap which is crimped on both of its ends. In flight, the rotation of the projectile ensures that the free-floating balls are held in contact with the ballistic cap under centrifugal force. When penetrating a metal sheet or relatively weak obstacles, like a masonry wall or a wooden log fortification, the nose spike of the fuze remains intact, penetrating the target by some amount, but as the ballistic cap follows the spike, it is crushed against the target medium, forcefully driving the balls onto the striker and causing the shell to detonate. This is shown in the drawings below. The top drawing depicts the fuze in an armed state, in flight towards the target. The bottom drawing shows how the ballistic cap is crushed when the shell has penetrated an obstacle, driving the balls onto the striker. When penetrating a thick metal barrier at a low obliquity, the base of the nose spike collapses under the stress, and the striker is driven onto the percussion cap by the nose itself rather than by the balls.

However, the foremost feature of the fuze is that by using balls held against the ballistic cap, the fuze is able to function reliably even on thin surfaces at grazing impacts on all barriers and obstacles, including the thin duralumin skins of aircraft. For a high velocity shell predominantly used on ground targets, grazing impact sensitivity was essential for reliable fuzing on flat ground, as the flat trajectory of the shells could otherwise cause issues due to the very low impact obliquity. In combination with the steel nose spike, reliable fuzing, favourable fuzing delays, and good penetration depths are obtained against a wide variety of targets.

It is stated in the 2009 book "Soviet Cannon" by Christian Koll that the A-670M fuze has a delay of 0.15 milliseconds, or 0.00015 seconds. This short delay is slightly longer than the nominal value for an instantaneous fuze (0.1 milliseconds), but is well within the norm for fuzes of this type. Based on how the fuze functions, it is likely that the stated delay is applicable when the target is a relatively soft obstacle, permitting penetration by the nose spike. Depending on the impact velocity and target obliquity, the shell will embed itself by some amount before detonating. For instance, when firing upon personnel in the open at 1 km, the fuzing delay of 0.15 milliseconds means that the shell detonates only after travelling 105mm after fuze initiation. Depending on the impact angle, the actual distance travelled into the ground tends to be around a few centimeters. As the fuze itself is 69mm long, the body of the shell itself is only slightly embedded into the ground, and the fragmentation effect is therefore worsened by a small amount. 

If the ground is flat, the shell impacts at a small obliquity, and the fuze functions in graze mode, which leads to quicker action. The shell does not embed deeply in the ground under such conditions, as the approach angle causes the shell to travel along the surface of the terrain rather than into it. The fragmentation effect is much less affected in this circumstance. 

The velocities of the 3UOF8 round at various distances are listed in the firing table shown below.

Though the HE-Frag fuzing mode produces a slightly worse fragmentation effect compared to a Frag fuzing mode, HE-Frag provides the necessary flexibility to engage a wide variety of threats with a greater overall effectiveness. The main advantage is in engaging thin-skinned vehicles, which require delayed fuzing to be efficiently destroyed, particularly when attacked from perpendicular angles (fragmentation to the front of the shell is minimal). The same rationale is applicable to aircraft as well, though the fuzing delay is somewhat shorter than most aviation shells, which have long delays to allow the shell to travel several times its own length for maximum destructive effect. Nevertheless, a Fragmentation effect is to be strictly avoided when firing upon aircraft, because surface detonations have a very poor effect on self-sealing fuel tanks and other protected assemblies. Lightly armoured vehicles such as APCs and MRAPs can also be engaged, with the expectation that the armour is at least perforated by kinetic energy, and potentially a wider hole can be blown through by the explosion, with strong post-perforation effects. The combined kinetic-explosive mechanism also allows the shell to cause serious damage to structures, which would otherwise not be feasible with a Fragmentation fuzing setting.

The photos below, courtesy of an unnamed Finnish BMP-2 mechanic, show the destructive effect of 30mm HE shells on a 10cm reinforced concrete wall with an additional thin brick-like facade during a live fire demonstration in Finland in 2013. The shells were able to knock out sections of the wall, creating relatively large loopholes. Of the three holes in the wall, one of them is smaller than the others - this was presumably created by the weaker OR2 shell which complements OF47. Naturally, weaker structures built from brick or concrete-filled cinderblocks are easier to destroy using such shells. It may be feasible to knock down walls or create man-sized entryways with a long burst of shots.

30mm HE shells also have the capability to destroy field fortifications with ease. For instance, the destroyed tree shown in the photo below was hit by a HE shell that missed the concrete wall during the live fire demonstration. A machine gun nest or command post protected by sandbags and logs offers little to no protection from direct hits by OF47.

Additionally, as part of these demonstrations, HE-I and AP-T rounds were fired at a 2.5cm steel plate. Two HE-I impacts are visible in the photos below. One shell hit the edge of the plate, creating a deep gouge, but the other was a fair hit. The penetration into the plate was deep enough to severely bulge out the rear surface of the plate. The depth of the scoring from the fragmentation effect appears to be comparable to the scoring observed on a T-72 turret tested with the same 30mm OF47 rounds, on display at Parola. Both hits on the turret were characterized by penetration and scoring of similar depth, as visible on the turret cheek and turret roof. From this, it is plausible that the steel plate was medium hardness armour.

In head-on impacts such as in these cases, the nose spike and short delay of the fuze is responsible for facilitating this type of damage. Otherwise, surface detonations on concrete walls and logs have minimal destructive effect. Thus, the fuzing capabilities of the A-670M can be considered the most conducive option for ground vehicles such as the BMP-2, which are routinely expected to fire upon all varieties of possible targets, ranging from infantry in the open, infantry in shelters and fortifications, cars, trucks, lightly armoured troop transports, and even carry out local air defence against both armoured and unarmoured aircraft if necessary. 

In the Soviet Union, S-10 and S-20 low-carbon steels (0.10% and 0.20% carbon content respectively) were used for small caliber cannons (autocannons), instead of the typical S-60 high-carbon steel (0.60%) used in artillery. A low carbon content degrades the fragmentation behaviour of the steel, so low-carbon steels used in the production of autocannon shells undergo additional processing including steps such as cold extrusion, which, along with increasing the strength characteristics of the steel, improved the fragmentation behaviour. This does, however, increase the relative cost of production because artillery shells made with S-60 steel were die-forged rather than extruded, and they were not heat-treated after forging, making them extremely simple to produce yet highly effective in fragmentation.

49 grams of A-IX-2 is used as the explosive filler in OF47. It is an aluminized high-explosive compound consisting of 73% RDX, 23% aluminium powder, and 4% phlegmatizer. The aluminium content increases the heat of the explosion and is responsible for generating the incendiary effect of the shell. The prolonged combustion of the aluminium particles serves to increase the explosive impulse, which is responsible for a good blasting effect. The peak temperature in an A-IX-2 explosion is 3,000°C. A similar design approach was applied in the 25mm M792 HEI-T shell, which is filled with a high-explosive incendiary compound with 64% phlegmatized RDX and 35% aluminium powder.

The A-IX-2 formula was invented in 1941 and production began sometime in the early 1940's. All Soviet autocannon shells manufactured after 1943 were filled with A-IX-2, but prior to that, generic explosive ammunition was filled with TNT and was split between two types: OZ (HE-I) and OF (HE-Frag). The best example is the 20mm ShVAK aircraft autocannon, which was supplied with a mix of OZ, OF and OFZ (HEFI) rounds. OZ shells were composed of a small HE filler with an incendiary pellet at the tip of the projectile, whereas OF rounds had a purely HE filler with fragmentation grooves, and OFZ was a hybrid of the two. The incendiary component was desirable for anti-aircraft purposes, whereas a higher explosive yield with increased fragmentation would be more optimal against ground targets. When A-IX-2 became available, all subsequent autocannons intended for all varieties and combinations of roles (air-air, ground-air, etc) were supplied only with general purpose HEFI shells incorporating A-IX-2, as it provided both a powerful high explosive effect as well as a secondary incendiary effect.

The length of the unfuzed projectile body is 145.8mm (4.86 calibers) and the wall thickness is 5mm (0.167 calibers) except in the tail section, where a variable thickness is present due to the annular groove for the driving band and the crimping grooves. The explosive filler weight proportion is 12.5%, which is very good, as it places 3UOF8 within the same class as medium to low-velocity artillery HE-Frag shells. Purely by mass, this is a better proportion than artillery shells such as the domestic 100mm OF-412, 76.2mm OF-350 or the American 75mm M48 HE shell - all of these have a filler proportion of 9-10%. In practice, the fragmentation efficiency is greatly bolstered by the use of an A-IX-2 filler rather than TNT, due to the greater explosiveness and brisance.

Compared to a 20x139mm (Hispano Suiza) HE shell, the caliber of the OF47 shell is only 50% larger, but owing to the square-cube law, the volume of each 30mm shell is larger by the cube of the scale factor. Because of this, OF47is 3.25 times heavier than a typical 20x139mm HE shell. The payload delivered by each 30mm shell is therefore considerably more potent than the caliber itself suggests.

Due to the quadratic nature of the increase in fragmentation effect with increasing caliber, 30mm HE shells were more than four times as effective compared with the typical 20mm HE ammunition used by NATO forces. The graph below, from the "Handbook on Weaponry (1982)" by Rheinmetall GmbH, shows the number of effective fragments produced by four different calibers of HE shell, represented by 20x139mm, 23x152mm, 30x170 and 40x365mm cartridges. In this case, "effectiveness" is rated by the ability of the fragments to perforate a 1.5mm steel sheet. Unsurprisingly, 20mm HE has very poor fragmentation characteristics, producing few effective fragments, and none that are capable of maintaining effectiveness out to 10 meters. In practical terms, this means that a soldier lying prone in the open is not likely to be hit by a fragment, and if hit, the fragment is not likely to be capable of delivering a lethal wound if he is wearing winter clothing or if he is situated behind light concealment. Compared to 20mm HE, Soviet 23mm HE is more than twice as effective, especially beyond 10 meters. Compared to 23mm HE, 30mm HE is again more than twice as effective (around 2.22 times), even out to 15 meters. 30mm HE would also be around twice as effective as 25mm HE (Oerlikon).

Based on the fragments collected from an aviation 30mm OFZ-30-GSh shell shown in a photo published in the book "Soviet Cannon", OF47 should produce around 134 pieces of large fragmentation, not including small fragments, dust or fuze fragments, of which the majority (by weight) was between 0.5 to 2.0 grams. The book mentions that the total weight of all recovered fragments was 327.2 grams, indicating that a considerable mass was missed; the total recoverable mass is 341 grams, including the fuze. The total recoverable mass from the casing is 292 grams. The aviation 30mm shell, designated as OFZ-30-GSh, differs from the ground forces shell only by having the AG-30 fuze, which is very similar to A-670M. The shell itself is identical to OF47.

Fragments weighing less than 0.5 grams are very numerous and possess enough energy to produce a casualty, but rapidly lose their energy within a few meters (particularly splinter-shaped fragments, due to tumbling) and as such, are limited in their ability to expand the lethal zone. Although 0.5 grams seems to be very light, it is important to note that a steel fragment of this weight will have a diameter of around 5mm; such fragments are quite appropriately classified as large fragments. Fragments weighing less than 0.25 grams are considered ineffective owing to their short range. When including fuze parts, there are a total of no less than 138 fragments above 0.5 grams in mass. The following lists the total quantities in each mass range. Unless specified, all were manually counted.

• ≥138* (9.72%) in the 0.1-0.24 grams range
• ~88** (10.76%) in the 0.25-0.49 grams range
• ≥63*** (18.43%) in the 0.5-0.99 gram range
• 57 (25.06%) in the 1.0-1.99 gram range
• 17 (11.43%) in the 2.0-4.99 gram range
• 1 (3.94%) above 5.0 grams

*There must be no fewer than 138 fragments weighing 0.24 grams to total 33.14 grams (9.72%). Only 97 pieces could be visually identified, which is far below the minimum required, indicating that the image is either not clear enough, or not all fragments are visible. It is only possible to say for certain that there must be at least 138 pieces. 

**The number of fragments was determined visually. There must be no fewer than 75 fragments weighing 0.49 grams to total 36.69 grams (10.76%). A total of 88 pieces could be visually identified, indicating that most of the fragments are in the upper end of the 0.25-0.49 range. 

***There must be no fewer than 64 fragments weighing 0.99 grams to total 62.84 grams (18.43%). Only 61 pieces could be visually identified, indicating that the image is either not clear enough, or not all fragments are visible. It is only possible to say for certain that there must be at least 64 pieces. 

(Note: The mass share of the fragments is always relative to the total mass of the shell body alone, the weights of the explosive filler and fuze are always excluded. In the book "Soviet Cannon", the fuze mass was included, making it necessary to normalize the data before it can be compared to other data.)

Of the remainder of the shell:

• 5.17% of fragments weigh 0.02-0.09 grams
• 2.17% of fragments weigh less than 0.02 grams
• 0.67% is dust

The total number of fragments weighing 0.5 grams or more is at least 139 pieces (excluding fuze pieces).

For comparison, the 30x170mm UIA (HEI) shell for the Hispano-Suiza HS.831 autocannon, the direct counterpart to Soviet 30mm ground autocannons. Oerlikon or Hispano-Suiza 30x170mm UIA (HEI) shells weigh 360 grams and contain a 40 g charge of Hexal P30. They are interchangeable, and can be considered equivalent. The shell has a casing mass of 288.7 grams. It produces 134 fragments weighing 0.5 grams and above, with a fragmentation distribution shown in the table below. The data for 30mm UIA is from "Fragment Mass Distribution of HE Projectiles" (1990) by Manfred Held. Fuze mass is excluded from the fragment mass distribution percentage in the OFZ column.

Fragment mass (g)	30x170mm UIA	30x165mm OFZ
>5.00	9 (22.4%)	1 (4.51%)
2.00-4.99	37 (27.4%)	17 (13.08%)
1.00-1.99	25 (20.9%)	57 (28.69%)
0.50-0.99	55 (13.5%)	≥64 (21.09%)
<0.49	589 (15.72%)	- (32.6%)

Owing to the incomplete fragment quantity data for 30mm OFZ due to the significant amount of unrecovered mass and the use of manual counting, the figures presented are likely smaller than the actual values, but nevertheless, the mass distribution data allows a direct comparison of the quality of the fragmentation behaviour of the two shells.

As the table shows, the fragmentation characteristics of the two shells are very different despite the gross similarities in paper specifications. The UIA shell expends half of its casing weight (49.8%) in very heavy fragments, weighing 2 grams and above, and the remainder is spent in a moderate quantity of medium-large fragments and a large quantity of excessively light fragments; 15.72% of the casing weight is expended in creating very small fragments, with an average mass of 0.077 grams, as determined from the given quantity. 

In contrast to this, OF47 generates a much more rational distribution of fragments, with a limited quantity of fragments that are very heavy and fragments that are very light. Rather, the shell produces a large number of medium-large fragments in the range between 0.1 and 2.0 grams. Within the range of light fragments - which are those weighing 0-0.49 grams - 63% lie within the 0.1-0.49 gram range. The weighted average mass of these light fragments is 0.21 grams, which is much higher than the 0.077-gram average mass of fragments in the same range produced by the UIA shell.

As a result of the more efficient fragmentation behaviour of the OF47 shell, it produces more fragments weighing 0.5 grams and above with a smaller proportion of the case compared to the UIA shell - merely 67.37% compared to 84.2%. As such, not only does the OF47 shell carry a larger and more potent explosive payload, but its fragmentation performance is also better optimized. Relative to the 3UOF8 round, the Hispano-Suiza 30x170mm UIA shell design traded a strong target effect for a flatter trajectory and shorter time of flight, superior to OF47 due to its higher muzzle velocity of 1,080 m/s. This reduced its time of flight to 2 km to 2.59 seconds as compared to the 2.9 seconds achieved by v. The self-destruct range was still the same, however - 4 kilometers.

Taking another 30mm shell for comparison, the 30x111mm Hispano-Suiza UIA Heavy shell for the ADEN autocannon - which is a 250-gram shell with a filler of 45 grams of Trinalite (aluminized TNT) - produces 89 fragments in the 0.5-1.0 gram range and 32 in the 1.0-2.0 gram range, for a total of 121. This surpasses OF47, and this can be credited to the higher mass proportion of its filler; 18% compared to 12.5%. In fact, the fragmentation efficiency is very high, because there is virtually no dust and there are extremely few pieces of fragmentation that weigh less than 0.1 grams, or at least appear to, by visual comparison. This can be seen in the photos below. 

However, these gains in fragmentation efficiency do not compensate for the fact that the shell body is much lighter and hence, produces fewer fragments overall; not counting the smallest pieces, there are only around 79 fragments weighing < 0.5 grams that are large enough to be identified in the photo, out of an actual total of 589. The total of ~200 pieces compares unfavourably with the 346 pieces produced by the OF47 shell. The 30x111mm Hispano-Suiza UIA Light for the ADEN, the lighter counterpart to the UIA Heavy, weighing just 228 grams while having a 50-gram filler of Trinalite, has a worsened fragmentation effect as it was deemphasized in favour of an improved blast effect, increasing its effectiveness against aircraft. Due to the thinned shell walls, the majority of the fragments produced are too small to be effective, and significant shell mass is lost to pulverization of the body into dust. Within the range of 0.15-0.5 grams, there are ~208 fragments (visually determined), in addition to only 16 fragments between 0.5-1.5 grams, and the remainder consists of either very light or very heavy fragments between 5-15 grams (base of the shell, fuze parts). This compares very unfavourably with OF47, which produces no less than 364 fragments in the 0.1-5.0 gram range. Thin-walled HEI shells, particularly mine shells such as the classic wartime 30x90mm Minengeschoß design for the MK 108, waste virtually all of their body mass in very small splinter-shaped fragments and dust, trading almost the entirety of their fragmentation effect for blast effect, making them highly specialized air-to-air ammunition. By moderating the explosive filler weight, this was largely mitigated in Cold War era high-capacity HEI shells such as the UIA Light and its British and French counterparts for the ADEN and DEFA respectively, as well as HEI shell designs that followed.

The fragmentation performance of the OF47 shell can also be compared with the GPD-30, which has a pre-scored casing designed to improve the mass proportion of medium fragments, suppressing the formation of small and very large fragments.

• 91 are in the 0.1-0.24 gram range
• 33 are in the 0.25-0.34 gram range
• 160 are in the 0.35-0.49 gram range
• 66 are in the 0.5-0.99 gram range
• 17 are in the 1-1.99 gram range

It can be seen that, despite weighing less, GPD-30 produces 367 fragments in the 0.1-1.99 gram range, whereas OF47 produces 346 fragments within the same range (if the fragments weighing above 2 grams are included, the total is 364 pieces). Due to the prescored casing, GPD-30 is able to produce a comparable number of fragments above 0.1 grams by controlling fragmentation behaviour to increase the share of fragments that have an optimum weight, and by eliminating the wastage of the grenade base, which is scored to allow it to fragment, unlike the OF47 shell. Moreover, excluding ineffective fragments, which are defined as those weighing less than 0.25 grams, it can be seen that GPD-30 produces 276 fragments and OF47 produces 226 fragments; even taking into account the uncertainties on the fragmentation data for OF47, the grenade shows a clear advantage. In combination with the superior ballistic performance of cubic or irregular fragments compared to splinters, the GPD-30 grenade actually creates a larger lethal area than the OF47 shell for any given impact angle, despite the large difference in overall projectile mass. In practice, GPD-30 has a substantially larger lethal zone due to much more favourable impact angles (owing to its low velocity) and a better fragmentation pattern.

According to data provided by Kurganmashzavod in the February 1993 issue of the "Техника и Вооружение" magazine, the area of nominal defeat against personnel lying prone on open ground is 70-80 square meters. The area of nominal defeat is defined as the area within which 50% of the personnel receive lethal wounds. Though it is not specified, this data was very likely to have been extrapolated based on a fragment arena test rather than a realistic live fire test at level ground. In real conditions, a large number of fragments do not strike targets on ground level due to the flat impact trajectory, especially because the brief fuzing delay causes the shell to detonate while slightly embedded in the ground. For comparison, the Soviet 85mm O-365K Frag shell has an area of nominal defeat of 130 sq.m against personnel lying prone on open ground, with a plunging impact angle of 20-40 degrees. It is extremely unlikely that a single 30mm HE-Frag shell reaches half the fragmentation effect of an 85mm Frag shell.

A similar figure is provided in the 1998 book "История создания и развития вооружения и военной техники ПВО Сухопутных войск России: Часть Вторая", where it is stated that the lethal area of a 30x165mm HE shell against personnel seated in automobiles on open ground is 82 square meters. This compares favourably to the 52-square meter lethal zone of a 23mm HE shell, but both are unrealistically high. Against personnel standing on open ground, the lethal area of a 23mm HE shell is 70.4 square meters and the lethal area of a 30mm HE shell is 110 square meters. 

For comparison, the GPD-30 grenade has a lethal area of 130.5 square meters against personnel standing on open ground. It is also interesting to compare it to the 25mm M792 HEI-T shell, as it is stated in MIL-PRF-71139A that the lethal area of a surface burst shall be 6 to 14 square meters against personnel using lethal area calculation procedures, in a 30-second defense situation, with personnel targets in the prone position with winter uniforms at 1,000 to 3,000 meters.

Against aircraft, with the Il-28 and MiG-17 to represent a medium jet bomber and a jet fighter respectively, the number of hits needed with 30mm OFZ is approximately half that of 23mm OFZ. Against a MiG-17, at least 1.4 hits are needed, whereas at least 3.0 hits are needed with 23mm OFZ. Against an Il-28, at least 2.8 hits are needed, whereas at least 6.0 hits are needed with 23mm OFZ. The difference in anti-aircraft effectiveness was primarily determined by the increase in the explosive charge mass delivered into the airframe.

Cartridge mass: 842 g
Cartridge case mass: 318 g
Propellant charge mass: 126 g  (other source gives 123 g)

Projectile mass: 390 g

Muzzle velocity: 980 m/s

Explosive mass: 49 g

Explosive filling: A-IX-2

If compared to the 25mm M792 shell, the OF47 projectile weighs 2.1 times more despite the small difference in caliber, while its explosive charge is only 1.53 times heavier. According to the square-cube law, the direct scale factor of OF47 in weight would only be 1.73 times, but due to radical design differences, the overall projectile mass and filler mass do not correspond to the scale factor. In terms of projectile weight, M792 is actually only equivalent to a Soviet 23x152mm HEFI shell. In fact, the M792 projectile design follows that of mine shells like the UIA Heavy examined earlier - it has a thick base but a thin wall around its filler, making it disproportionately light and short for its caliber while having a heavier filler. 

Additionally, due to its good ballistic coefficient (primarily due to its larger weight, slender form and high aspect ratio), the 30mm OFZ shell has a flatter trajectory and a shorter time of flight than M792 out to 2 km (2.9 seconds vs 3.3 seconds) and beyond despite having a lower muzzle velocity by 120 m/s. This is despite its flat base and lack of tracer, which increases base drag.

In terms of the weight of the payload delivered to a target and the resulting blast and fragmentation effect, OF47 nominally surpasses other 30mm HE shells. In practice, the firepower advantage may be particularly pronounced due to other considerations. For example, the RARDEN clip-fed autocannon did not use HEI shells at all, having only HEI-T shells. Due to the low rate of fire, a full tracer load was needed to fulfill basic fire correction requirements at the expense of the target effect. The L13 HEI-T shell for the 30x170mm RARDEN is reported by Jane's to have a Torpex 2 explosive filler weighing just 25.6 grams. The earlier L8 shell for the RARDEN also weighs 360 grams but contained just 20 grams of Hexal P30 (Hispano-Suiza UIAT).

3UOF8 rounds are loaded in a 4:1 ratio to 3UOR6.

F-T (OT)

3UOR6

OR2

  

3UOR6 is a high-explosive incendiary fragmentation shell with a tracer. It was intended to complement 3UOF8 for fire correction purposes. The A-670M nose fuze is used. Officially, the 3UOR6 round is designated as an "ОТ" (Осколочно Трассирующий), or fragmentation-tracer (F-T) round, and this is because its small explosive charge makes it unsuitable for high explosive and incendiary action. As such, its only practical tactical role is to defeat infantry and soft-skinned vehicles in the open, but even then, with greatly reduced efficacy compared to OF47.

The tracer has a burn time of no less than 10 seconds, allowing precise fire correction out to a range in excess of 4,000 meters, which is the lower boundary of the self-destruction range. The need for a massive tracer came from the development of the BMP-2, when the tactical niche of autocannons had to be rather wide to justify its use instead of a 73mm low pressure gun. One of the niches for the prospective 30x165mm autocannon is that it was envisioned as having the capability to engage ATGM emplacements out to a range of 4,000 meters. The premise of this method of engagement is that the gunner would fired short bursts at an ATGM position and use the single HEI-T shell to observe the trajectory of the entire burst. The target effect of the full burst, which would be a cluster of successive explosions, can also be observed clearly from long range. 

This is in contrast to the ammunition design of slow-firing autocannons like the 25mm M242, where only HEI-T is used. This practice is also more common in aviation or anti-aircraft ammunition where each and every round has a tracer, due to the much more dynamic nature of engaging air targets. For slow-firing ground autocannons, the low rate of fire (for the M242, 100 RPM or 200 RPM) makes it difficult for a single tracer shell to effectively trace the trajectory of a burst. As such, weapons like the RARDEN and M242 were only supplied with HEI-T shells instead of a HE-I and F-T mix. Because of this, an excessively large tracer could not be fitted without severely compromising the payload of the shell, and in turn, this meant that the tracer burnout range had to be limited. For 25mm HEI-T shells, it was limited to only 2,000 meters, only two thirds of its maximum range of 3,000 meters. The Soviet equivalent to this type of shell is the aviation 30mm OFZT-30-GSh shell, which is very similar to 3UOF8 except that it has a tracer, accompanied by a reduced filler weight of 43.3 grams. Due to the much short ranges feasible for aircraft autocannons, having a limited burn time of 1.5 to 4.0 seconds and a tracing range of just 1,200-2,400 meters was justified, and a full load of HEI-T ammunition was reasonable when firing on air targets.

A more direct, and particularly meaningful comparison can be made with the 23mm OFZT shell, as that has a much smaller tracer with a burn time of no less than 5 seconds. This allowed fire correction out to a maximum range of 2,500 meters, which is the maximum slant range of the ZU-23-2 against air targets as per the tactical-technical specifications, which is worth noting as the maximum horizontal firing range is considered to be only 2,000 meters (nominal time of flight of 3.86 seconds). The much smaller size of the tracer can be seen in the cross section of the 23mm OFZT shell (left below) relative to the 30mm OT shell (right below).

The shape of the OR2 projectile body differs from the OF47 shell in that the center is cut to a smaller diameter, to offset the weight added by the internal partition dividing the explosive charge from the tracer element. This forms a distinct waist, resembling WW2-era "arrowhead" APCR projectiles. The thicker upper and lower sections of the projectile serve as centering bands as the projectile travels down the barrel. The length of the OR2 projectile is 145.8mm (4.86 calibers). The length of the tapered nose section is 70mm (2.33 calibers). The remainder of the projectile is cylindrical. The maximum wall thickness is 5mm (0.167 calibers), the same as OF47, though the shape of the cavity for the explosive filler is different, being a simple cylinder. 

Due to the very large tracer element carried in the projectile, the weight of the explosive charge was reduced to just 11.5 grams. This is less than the 13-gram payload of a 23mm HEFI-T shell, and is roughly equal to a 20mm HE-I round. For instance, the M56 round had an explosive-incendiary charge with a total weight of 12 grams. This ostensibly gave the shell an extremely poor charge weight proportion of just 2.9%, but this does not correctly reflect the fragmentation behaviour of the shell, because this implies that the casing wall is extremely thick for the filler. In fact, the filler is simply contained in a shorter cavity, surrounded by a casing wall with the same thickness as on OF47. The fragmentation behaviour of the casing should therefore be similar, producing fragments of similar size and energy, only differing in quantity. However, in practice, the fragmentation effect on open ground can be much worse, because it is possible for the nose of the shell to embed in the ground if the graze function is not triggered. With the filler being contained entirely within the front half of the projectile, the worsening of the casualty area can be more pronounced for the OR2 shell. According to figures given in the textbook "Средства поражение и боеприпас: Учебник" (Means of destruction and ammunition: a Textbook) by the Bauman Moscow State Technical University, 3UOR6 produces several dozen fragments, with a mass of 1 to 10 g and a velocity of 1,100-1,200 m/s.

According to data provided by Kurganmashzavod in article "Производственное объединение Курганского Машиностроительный Завод" published in the February 1993 issue of the "Техника и Вооружение" magazine, the area of conditional defeat against personnel lying prone on open ground produced by an OT shell is 25-30 square meters, much less than the OFZ round, but around the same or slightly more than a 25mm M792 HEI-T shell. 

Cartridge mass: 835 g
Cartridge case mass: 318 g
Propellant charge mass: 126 g (other source gives 122 g)
Projectile mass: 388 g

Muzzle velocity: 980 m/s

Explosive mass: 11.5 g
Explosive filling: A-IX-2

Tracer burn time: 14 seconds

AP-T (BT)

3UBR6

BR3

  

3UBR6 is an armour-piercing round with a tracer (BT). It was the standard AP round for the new 30mm autocannon system for ground forces. The BR3 projectile was designed to defeat only lightly armoured targets, with the M113 being the most commonly cited example of a typical APC target. During the Cold War, it was sufficient for most IFVs and APCs due to the modest protection standards of this class of armoured vehicle. It was also capable of disabling some Western tanks to some extent, particularly when attacking from the flanks or the rear, but only from close range.

It is unclear why it did not have an incendiary element in its nose, like the 23mm 3UBR1 armour-piercing incendiary (BZT) round for the 2A14 autocannon that preceded it.

The BR3 projectile has a unique double conical tip that is distinct from practically all other blunt-tipped armour piercing rounds used in the USSR. The tip of the projectile can be seen in the photo below. It most closely resembles the tip of the tungsten alloy core of an L52 APDS projectile.

The armour-piercing body of the projectile is made from 35KhGS structural steel. It was heat-treated to a hardness of 47-56 HRC (451-552 BHN). As is typical for this type of penetrator, the softest areas are at the base and center and the hardest areas are the nose and the penetrator body surface around the midsection. The weight of the entire projectile, including the driving band, tracer element and ballistic cap, is 400 grams. The weight of the steel core alone is 375 grams.

As the drawing above and photo below shows, the base of the shell has a large flared cavity with a tracer element embedded deep within. The tracer burns for no less than 3.5 seconds and will remain visible at no less than 2,300 meters. The most noteworthy consequence of this design feature is that the gasses released by the burning tracer element will expand in the flared section. From there, a gas stream is formed behind the projectile instead of a turbulent wake, causing a significant reduction in base drag. This reason is likely to be the explanation for the noticeably better energy retention of the BR3 projectile compared to the OF47 shell, with it having an impact velocity of 546 m/s at 2,000 meters, while the OF47 shell has an impact velocity of 472 m/s at the same range. Compared to an AP-T projectile with a conventional placement of the tracer, some advantage in energy retention can still be expected, but with a diminished margin.

Although there is no incendiary element in the projectile, the large tracer element has considerable fire starting potential against armoured vehicles as it would be ejected through the other side of an armour plate along with penetrator fragments. This effect can be quite strong if the round is fired against targets at typical combat distances of less than 2 km, as the tracer would remain only partially consumed at the point the projectile hits the target. Nevertheless, it is quite weak compared to the 23mm 3UBR1 BZT round, as that not only has a large incendiary pellet in its nose but also a heavier tracer element that burns for no less than 5 seconds, thus ensuring a much more powerful incendiary effect on both armoured and unarmoured targets.

With a muzzle velocity of 970 m/s under standard conditions (charge temperature of +15°C), BR3 can be considered to have a respectably high velocity. Nevertheless, due to the nature of the round, its point blank range of the round against many armoured personnel carriers was still quite modest. Referring to the firing table shown below, the point blank range of BR3 against an M113 with a structural height of 1.42 meters is only around 920 meters. Against an M2 Bradley with a structural height of 2.1 meters, the point blank range is around 1,120 meters. Against a Marder 1 with a structural height of 1.86 meters, the point blank range is around 1,080 meters.

According to the article "Боевая Машина Пехоты" published in the April 2001 issue of the "Техника И Вооружение" magazine, the probability of hitting an APC-type target (M113A1) at a distance of 1.5 km with a burst of BT rounds is 0.55.

Besides the penetration values provided by various sources, presented below, it is also stated in the paper "Использование Металл-Фторопластовых Композитов в Малокалиберных Боеприпасах Ударно-Проникающего Действия" by Alekseev et al., published in the All-Russian Scientific and Technical Conference, that the 30mm BT shell has a perforation limit of 815 m/s on a 35mm plate of St21 steel. This is presumed to be on a flat impact angle, but is more likely to be between 30 degrees and 60 degrees. From the firing table shown above, it can be seen that a velocity of 815 m/s corresponds to a range of 700 meters. 


Cartridge mass: 856 g
Cartridge case mass: 318 g
Propellant charge mass: 126 g (other source gives 127 g)
Projectile mass: 400 g

Muzzle velocity: 970 m/s

Penetration, RHA (60 degrees):
700 m = 20mm
1,000 m = 18mm
1,500 m = 14mm 

(Official values)

Penetration, RHA (60 degrees):
500 m = 22mm
1,000 m = 18mm
1,500 m = 14mm 

(Bulgarian copy) 

Penetration, RHA at 300 m:
60 degrees = 26mm
65 degrees = 23mm
70 degrees = 20mm
75 degrees = 17mm   

(1983 Soviet study) 

The steel core in BR3 has an L/D ratio of 4.25. The lack of an armour piercing cap is a liability if the target plate is heavily sloped or preceded by spaced armour, but can increase the efficiency of penetration at flat or near-flat angles (30 degrees). However, the small increase in flat angle penetration from the lack of an armour piercing cap cannot be seen as a positive feature, as there are very few circumstances where the minor improvement in flat angle penetration would actually be useful. Indeed, the frontal armour of all APCs and IFVs feature well-sloped surfaces.


Due to its mediocre properties, its performance on light armour is rather modest, although it is certain that it is fully capable of perforating the armour of lightly armoured APCs such as the American M113, German Fuchs, French VAB, or perhaps the generally light armour of scout cars and other armoured cars, while some modern vehicles like the Stryker and LAV III still prove totally vulnerable, being no better armoured than their tracked peers from the 60's and 70's. It is capable of handily defeating certain zones of older IFVs like the Marder 1A2 and M2A1 Bradley from the front at ranges in excess of 1,500 meters, and the most heavily protected parts at closer ranges, but against the latest IFVs or IFVs specifically beefed up against it like the M2A2 Bradley and Marder 1A3, the 3UBR6 round is, for the most part, less useful than HEI shells. Furthermore, composite armour kits such as MEXAS can be fitted to many older vehicles, severely limiting the usefulness of 3BR6 even against outdated APCs.

It quite interesting to note that this shell should be able to perforate the side armour of some tanks of its time, particularly at close ranges. The AMX 30, Leopard 1 and Chieftain are three such unfortunate examples. Legacy tanks like the Centurion are highly vulnerable as well. However, achieving this feat does require the autocannon to be set up in an ambush position with opportunities to attack the flanks of the aforementioned tanks at a very favourable (perpendicular) angle.

There is some news that new ammunition incorporating plastic driving bands has been put into service in the Russian army. 3UBR10 matches this description, but its status remains largely unknown at the moment. The only difference between 3UBR6 and 3UBR10 is the replacement of the copper driving band with two nylon ones. You can see such driving bands here (link). Copper driving bands on a normal pressure round like 3UOF8 and 3UBR6 is equal to 1 EFC (Effective Full Charge). The 3UBR10 round is apparently 3 times less harsh on the barrel.

APDS-T (BPS)

3UBR8

53-BM54

  

3UBR8 was derived from a naval APDS round codenamed "Kerner". It is a much more capable armour-piercing round, consisting of a tungsten alloy core carried in a plastic discarding sabot with an aluminium plug. Its capabilities are superior to the 3UBR6 by a wide margin in all respects, including practical accuracy. A higher velocity and superior ballistic coefficient enables the subcaliber projectile with its tungsten alloy penetrator to travel with a flatter trajectory and to retain more of its energy at extended distances. However, like all known APDS rounds for small caliber autocannons, the penetrator in the 53-BM54 projectile lacks an armour-piercing or dampener cap for improved performance on oblique targets and improved resistance to spaced armour targets. The only design solution implemented to address this issue was the use of a short conical nose on the penetrator as opposed to an ogived nose.

According to the article "Боевая Машина Пехоты" published in the "Техника И Вооружение" magazine, April 2001 issue, the probability of hitting an APC-type target (M113A1) at a distance of 1.5 km with 3UBR8 is 0.7, which is an improvement over 3UBR6 (0.55).


Muzzle velocity: 1,120 m/s

Cartridge weight: 765 g
Cartridge case mass: 318 g
Propellant charge mass: 136 g (other source gives 140 g)

Projectile weight (incl. sabot): 304 g

Penetrator core weight: 222 g

Core: Tungsten alloy

Penetration, RHA (60 degrees):
1,000 m = 35mm
1,500 m = 25mm
2,000 m = 22mm 

(Official values from Rosoboronexport and Kurganmashzavod)

Penetration, RHA (60 degrees):
100 m = 45mm
200 m = 40mm
500 m = 33mm
1,000 m = 28mm
1,500 m = 25mm
2,000 m = 22mm 

(Values from armyman.info)

Penetration, RHA (60 degrees)
1,000 m = 27mm
2,000 m = 22mm
4,000 m = 12mm

(Ordnance and Munitions, 21st Century Encyclopedia: Russia's Arms and Technologies, Chapter 7, light ground artillery ordnance) 

Tracer burn time: >1.5 seconds

The 3UBR8 round was not only a direct Russian counterpart to the L14A3 APDS round for the British 30mm L21 RARDEN but also resembled it in both penetrator design and in projectile weight. The L14A3 projectile assembly, including its sabot, weighs 300 grams - only 4 grams less than the 3UBR8 projectile including its sabot. The L14A3 projectile itself weighs 235 grams, so after subtracting the weight of its ballistic cap and tracer, the weight of its core should be practically the same as that of the 3UBR8. Due to the presence of an incendiary filler under the ballistic cap of the L14A3 projectile, it is possible that the L14 series had a lighter tungsten alloy core than the 3UBR8 which had a hollow ballistic cap; in a 1996 paper from the Polish Military Institute of Armament Technology, a penetrator mass of just 200 grams was cited for the L14A2 projectile. In practice, the difference in core mass would likely be compensated by its higher muzzle velocity of 1,175 m/s. It is worth noting, however, that the real difference is slightly smaller because British ordnance is usually tested at a propellant temperature of +21°C whereas Soviet and Russian ordnance is tested at +15°C.

Compared to the M791 APDS shell for the 25mm M242 autocannon of the M2 Bradley, which has a projectile weight of 134 grams inclusive of the sabot and a penetrator core weight of 104 grams, the 53-BM54 projectile with its sabot weighs 2.27 times more and the penetrator core weighs 2.13 times more. It is slower, having a muzzle velocity that reaches only 83.3% of the M791, but even so, 3UBR8 delivers twice the amount of kinetic energy to the target.

Due to the lack of an armour-piercing or dampener cap, the tungsten alloy penetrator is unprotected from spaced or composite armour, which is also a characteristic of other APDS designs for small caliber autocannons. Overall, 53-BM54 is on the same technological level as the 25mm M791 APDS and 30mm RARDEN L14 APDS. Because all of them have an uncapped tungsten alloy penetrator in a plastic sabot, they are not comparable to modern APDS shells for tank guns. Their performance degrades more rapidly on sloped armour, and they are more vulnerable to spaced or composite armour.

The 3UBR8 round provided a noteworthy firepower upgrade and gave Russian vehicles armed with 2A42 or 2A72 autocannons an enhanced capability against existing IFVs, but with varying degrees of success. IFVs like the M2A2 Bradley and Marder 1A3 were vulnerable at short ranges at various parts of their frontal arc, albeit not from the direct front.