Highlight of the Week

This week's highlight is an excerpt from an unpublished BTR-82A article.


2A72


Armed with a 30mm rapid fire autocannon in the BPPU oscillating turret, the BTR-82A blurs the line between what is traditionally considered an armoured personnel carrier and an infantry fighting vehicle. The turret itself has the upshot of totally separating the gunner from the weapons suite, thereby substantially reducing acoustic fatigue as well as completely eliminating the ingress of fumes from the firing of weapons. This creates a more conducive environment for the gunner to conduct his duties. However, these benefits seem rather lackluster in the face of modern unmanned turret designs like the Kongsberg MCT30 used on the upgraded Strykers in Eastern Europe. In truth, the BPPU turret is very similar to its host platform in that both are relics from from bygone days.




The 2A72 is a long recoil operated dual-feed autocannon. In its mount on the BPPU, the 2A72 can elevate to an angle of exactly +69°33' degrees and depress by -4°30' degrees. The cannon has two modes of fire. On the 'high' setting, the maximum rate of fire is 350 to 400 rounds per minute. In the 'low' setting, this is electronically reduced to around 200 rounds per minute. The gunner can switch between these two modes from his station.

As the cannon is mounted externally, it is not possible to directly access it from within the BTR-82A, but it is still possible to manually cycle the bolt from the gunner's seat. This is done via a pulley and ratchet system. A sheathed cable runs from the bolt of the 2A72 cannon down to a ratchet mechanism beside the gunner's seat. The handle is pumped upwards to work the bolt incrementally.




This system enables the gunner to clear jams remotely from his station.


As mentioned before, the 2A72 is a dual feed autocannon. Two belts of different ammunition types are fed into the cannon from the left, through the left side of the turret. Take a look at the GIF below (from this video):





Like any other vehicle-mounted autocannon, the 2A72 features forward ejection. The photo on the left shows a BTR-80A turret with its OU-3GA2 IR spotlight and old style shell casing ejection chute. The photo on the right shows the updated BTR-82A turret with the new upturned ejection chute.




The receiver assembly of the 2A72 is extremely compact. The entire cannon weighs only 84kg as a whole, nearly half that of the Mk44 (160kg), a contemporary 30mm chaingun. The barrel weighs just 36kg and measures 2500mm in length. The entire unit is 3006mm long. The excessively light weight of the gun can be a serious problem. The thinness of the barrel and the nature of the long-recoil operating system badly affects accuracy, especially if the cannon is fired without pause on full auto for extended periods, leaving no time for the barrel to cool. Not only does it result in inherently poor accuracy, it can result in the elongation and warping of the barrel, possibly leading to a rather dramatic droop. This, again, is not beneficial to accuracy.




It's good to have superior firepower, of course, but it must be said outright that the 2A72 on its own is an extremely silly choice of armament. Without props or a support frame around the barrel of the cannon to hold it steady, the 2A72 is extremely inaccurate. Promotional material claims that the 2A72 is effective against ground targets at a range of up to 2000 m and 4000 m against area targets, but these claims are not to be taken at face value, because these values are simply the biggest numbers marked on the range scales for AP and HE ammunition in the TKN-4GA-01 sight.







Using that single three-round burst as our data set, we can calculate that at 1000 meters, the grouping of those three shots will measure 4.6 meters between the furthest points of impact. This is equivalent to 4.6 angular mils. This is quite variable, as the cannon is not just inaccurate, but also not very consistent, so as a rule of thumb that the 2A72 should have an accuracy of between 4 mils to 5 mils when firing in bursts of three. The likelihood of scoring a hit increases if more rounds are put down range, but if the burst were longer, or if more bursts were fired in succession, the accuracy will degrade even further, so unless the gunner is prepared to expend half of his ammunition in one go, he should try to fire in semi automatic.


The lackluster accuracy of the 2A72 cannon has not gone unnoticed by the various militaries that employ it. For example, the Ukrainian KBA-105 "Shkval" turret used in the BTR-3U and the BM-7 "Parus" RCWS for the BTR-4 both mount a 2A72 with a rigid frame to support the barrel. Looking Eastward, we see that Chinese armoured vehicles like the ZBD-05 and ZBD-09 mount a 2A72 with a rigid frame built around the barrel in a shared turret design. The only example of a Chinese IFV turret with an unsupported 2A72 cannon is the turret from the Type 86A/G, which also ended up being used in the airborne ZBD-03, but with a slightly modified cannon barrel. As you can see, the barrel of the 2A72 on the ZBD-03 distinctly lacks the two oversized rings. From what we have seen of the newer Chinese IFV designs, we can rightly assume that the unsupported barrel configuration in the Type 86A/G was because it was an early effort to produce a domestically designed one-man turret, and that turret was later used in the ZBD-03 only because it happened to be small enough.

Russian engineers knew of the problem since the very beginning. The 2A72 was first used in the BMP-3, which was adopted in 1987, and by then the cannon was already mounted in a sleeve attached to the coaxial 100mm 2A70 cannon. The 2A72 would later be installed in early demonstrators of the Pantsir S, but the irrational configuration (insufficient accuracy and volume of fire) was quickly replaced with the same quadruple 30mm gun system as the Tunguska. The Bakcha-U turret  Recent projects like the Uran-9 UGV and the upgraded Tigr-M have their 2A72 cannons installed with a full-length sleeve around the barrel. The upgraded Tigr-M shares the same sleeve as the ABM-M30M3 RCWS used in the latest prototypes of Uran-9. Another example is the "Vikhr" UGV tech demonstrator based on the BMP-3, which features the ABM-BSM30 RCWS, also mounting a 2A72 in a support sleeve. The 2A72 on the BTR-82A itself might be given its own support sleeve in the future, as we have seen in an unnamed experimental variant, shown in the photos below.






The subcalibre nature of APDS ammunition will yield better results than full caliber HE rounds, so by right, the 2A72 should have an accuracy of between 3 to 4 mils with APDS when firing in bursts of three. With controlled single shots, then, the cannon should be capable of scoring a hit on an APC-sized target at moderate distances. Sustained full automatic fire is useful - and only useful - for the suppression or destruction of area targets such as infantry in the open, or infantry under cover, or the destruction of low and slow aircraft. At closer ranges of 200 to 300 meters, full automatic fire is highly recommended. Take a look at the devastation that this cannon is capable of:






At night, the maximum effective range of shooting hinges on the capabilities of the sighting unit.


The barrel of the cannon is installed into a sleeve at the end of the receiver assembly, and threaded in place.





It seems reasonable to assume that the barrel can be swapped out in only a few minutes in the field. As the two workers in the photo above are demonstrating, no special tools are needed.


The autocannon is supplied with 150 rounds of APDS ammunition and 150 rounds of HEI-T and HEI ammunition for a total of 300 rounds. This isn't as much as what the BMP-2 or the BMP-3 carries, but this is double the ammunition load carried by rivals like the Stryker with the MCT30 turret. In some situations this might compensate for the incredible inaccuracy of the cannon and the absence of advanced ammunition, such as airbursting shells, but when it comes to sustained firefights,


Loading the cannon is done partially from the outside of the turret.



Loading the first round, or clearing a misfired round from the breech of the 2A72 can be done manually or with a pyrotechnic charge in the case of a misfire.

It's worth noting that old and obsolete 3UBR6 steel AP-T ammunition is not supported in the BTR-82A, as evidenced by the use of a 2 km range scale which is used for APDS ammunition, as opposed to a 1.6 km one, which is for AP-T. APFSDS rounds are also not supported.

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