ArmenT wrote:Aditya_V wrote:
This is pure BS, the real reason it was deceided to go for 5.56*45 Ammunition was lessons from the Sri Lanka operations where the SLR was too cumbersome for close combat with high recoile compared to the 7.62*39 Type 56 rifles LTTE employed. but problem with 7.62*39 is because bullet tends to drop it is very inaccurate above 100 meters and not very effective in 100-500 meters conventional combat requirement. But the 5.56*45 mm cannot drop a Jihadi unless it hits a vital area where the 7.62 *39 and 7.62*51 can smash a femur bones etc even it hits legs/arms etc.
7.62x51 mm. cartridges produce a lot of recoil, which make the shooter lose accuracy in burst and full-auto mode. Also, they are much heavier. A user can carry nearly 2x the number of 5.56x45 mm. cartridges for the same weight of 7.62x51 mm. cartridges. Which are two reasons for going for the lighter cartridge.
Most of the debate between 5.56x45 vs. 7.62x39 has to do with the terminal ballistics of their respective bullets. The smaller and lighter 5.56x45 cartridge bullet has a flatter path and carries enough velocity at the 600 meter mark to penetrate through 60s era Soviet body armor (which is when the cartridge was selected). The 7.62x39 cartridge (also called M43) moves slower and loses a lot of velocity beyond the 100 meter mark.The wounding capabilities of its bullet are also different. At ranges of about 100 meters or so, the 5.56x45 mm. cartridge (also called the M855) bullet will fragment upon hitting a body and the fragments will separate and spread out, producing a bigger hole than 5.56 mm diameter and increasing the chance of hitting vital organs and such. Above this distance, the fragmentation possibility diminishes rapidly (allegedly M855 frag. capability was designed keeping some Geneva convention protocol in mind). So if a target is hit at say 400 meters, very good chance that the hole produced will stay at 5.56 mm. diameter and therefore, unless the bullet is aimed at a vital spot, the chance of stopping the target is lessened. The M43 bullet doesn't fragment at all, but due to the way it is balanced, when it hits soft tissue, the bullet travels about 10 inches in and then starts to yaw significantly, thereby increasing the size of the wound and the wounding potential. It does not lose this yawing ability at greater ranges, even though it starts to lose accuracy and velocity more rapidly. However, note that it needs to have significant penetration depth before yawing happens. In many situations, the bullet enters and exits before it has a chance to yaw, therefore only leaving a 7.62mm. diameter hole. Many studies of woundings from the Vietnam era to the 80s showed that this situation happened in the majority of cases. This greatly reduces the wounding potential of the M43 to around the level of a small handgun cartridge with non-expanding bullets. Which means that unless it is aimed at a vital spot, the M43 also has much less wounding potential in many cases. So unless it is aimed at a femur directly, a shot to the arm or leg isn't going to do do much.
However, due to heavier weight of the M43 bullet, it has less chance of deviating when fired through light foliage and leaves (i.e. behind cover), whereas the M855 bullet can get deflected by so much as a bee getting in the way of the bullet.
So what is to be done? Turns out that people have improved the original bullet designs. For instance, some other cartridges in the 7.62x39 mm. caliber include the M67 (Yugoslav), Chinese, Czech and other cartridges were developed well after the M43. In these designs, the bullet starts to yaw much sooner (in like 3 inches of penetration or so) and therefore, the wounding potential is more when using these cartridges. Similarly, the US military recently went with the M855 Mark 1, where the bullet has a much better chance of fragmenting even at ranges well past 100 meters and the US military are reporting much success with the improved cartridge. The Russians abandoned the M43 and went with the smaller 5.45x39 mm. cartridge since 1974 (when they replaced the AKM with AK-74) and the bullet in this cartridge also yaws and tumbles a lot easier, producing much larger wounds than 5.45 mm diameter holes. In fact, during the Soviet invasion of Afghanistan in the early 80s, the Afghan Muj used to call the 5.45x39 mm. bullet as the "poison bullet" on account of the fact that it produced much larger wounds than its size indicated (well that, and lack of quality medical care meant wounds were often fatal in a few days).
ArmenT - thank you for this wonderful and very informative post. Helped me to understand the issue in detail. It is posts like these which make it worthwhile to visit BRF.