The Government of India recently announced procurement of 72,400 units of US made Sig Sauer 716 G2 – 7.62×51 mm Assault rifles, 94,000 units of UAE made Caracal 816- 5.56×45 mm Carbines and over 7 lakh units of the Russian AK 203 7.62×39 mm SLR to be made in a new Indo-Russian joint venture Ordnance factory at Amethi.

The reversal back to the 7.62mm bore reflects the changing nature of battle dynamics of the Indian Army who had shifted to the “NATO” bore of 5.56 X 45 mm in early 1990s, with the INSAS SLR rifles. The INSAS SLR rifle was of indigenous DRDO design that had replaced the 7.62 X 51mm Ishapore SLR widely considered as a copy of the FN FAL L1A1 7.62 X 51mm rifle developed after the 1962 war to replace the World War 2 vintage Lee enfield .303” (7.7X56mm) rifles. The 7.62 X 51mm Ishapore SLR remains the best of all the rifles made to date by OFB Ishapore both for field reliability and workmanship, however it had to ultimately give way to the INSAS SLR due to the gun weight, gun length, recoil energy and flash. The INSAS SLR could never gain the kind of acclaim by the users in the Army despite the claims of the OFB. Finally with the rejection of OFB Ishapore’s Excalibur design rifles, the Indian Army’s next generation of Infantry Personal Weapon Systems are not going to be of indigenous design putting a huge question mark over the OFB Ishapore units comprising of Metal & Steel Works and the Rifle Factory.

There needs to be a greater awareness even in the civilian space about the basic capabilities of different rifles, for it is only with such awareness that the countries’ indigenous units such as OFB can design and manufacture world class weapon systems.

The adoption of these new multi calibre rifles by the Indian Army reflects the realization that the different theatres of the battlefield need different weapon systems or as the saying goes- “Horses for courses”.A relative comparison of typical dynamics of the 3 different rounds of ammunition in standard rifles are given below.

It is apparent from these dynamics that the 7.62 X 51 mm rifle packs the most amount of Kinetic Energy and has the highest killing capacity based on the momentum of the travelling bullet. The effective range of this type of rifle is around 800 yards (731 m). From the numbers procured it is apparent that this rifle is not going to be a standard issue, and meant for only sharp shooters of a unit.

It is interesting thereafter to understand the switching criteria which weighed in prompting the switch between the 5.56 X 45 mm INSAS SLR to 7.62 X 39 mm AK 203. Given below is the comparative ballistics performance of these two calibers from albeit different models of weapons but with similar dynamics.

Velocity & Trajectory

The 5.56 X 45 mm is high velocity round with a lower recoil, more tailored to semi-automatic or automatic firing in field. Infact the intent of this weapon is not to kill the adversary but to injure bad enough so that couple of other buddies are morally induced to tend to the wounded. However though the 7.62 X 39 mm has a lower muzzle velocity, it packs a greater killing power due to the higher bullet weight, and at 500 yards they hold on to their velocity much better whereas the 5.56 X 45 mm bleeds off at a more rapid rate.

The trajectory of a bullet on the other hand is a measure of its retention of elevation compared to the distance travelled. The more the elevation of the bullet drops, the bigger the adjustments that are required to be an effective shot and the harder it is to be accurate on a  consistent basis without a lot of practice. The long range trajectory of a 7.62 X 39 mm is poorer but the killing capacity at up to 200 yards distance is what ticked the box for the soldier.

The Kinetic Energy and the Momentum of the bullet on the other hand is a measure of the stopping power and killing capacity of the bullet. Given below is the comparative momentum of these two calibers.

As can be seen from the numbers the 7.62 X 39 mm round has a higher terminal momentum at its most effective range of up to 300 yards. Given that it is a wider round, its kill capacity is obviously greater.

Summarising the two calibers of weapons, while the 5.56 X 45 mm has a higher velocity and flatter trajectory it is really the most effective at close quarters and perhaps that is justifies its selection as a carbine which is an automatic weapon meant for close quarter battle (CQB). The 7.62 X 39 mm on the other hand has a higher kill capacity at up to 300 yards which the ordinary soldier wanted. Modern Battle fields require many other calibers and functionalities. Sniper Rifles are increasingly important to eliminate selected opposition. These rifles need to have a greater range and possess more kinetic energy and momentum rendering higher killing power. Area Domination weapons like machine guns with a high rate of automatic firepower, mortar, grenade and rocket launchers are other weapon systems that form a standard issue to any infantry unit.

It is important in a large country such as India for citizens from every walk of life to have basic awareness of such systems to bring about transparency and efficiency in the country’s weapons procurement and manufacturing process.

Image Credit

References : Sniper Country | Ammunitiotogo



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