MTMilitiaman
Member
Even the 77 gr is only 683fp at 300 yards.
steve
Yes, but it also still has 2100 fps or so of velocity.
Your typical 7.62x39 load shoots a ~125 gr bullet @ ~2350 fps. This is a light for caliber projectile with a terrible BC and it sheds over 300 fps in the first 100 yards. By the time you reach about 120 yards the bullet is dropping under 2000 fps.
A 75-77 gr OTM round in a 5.56 is a much heavier for caliber projectile with a much better BC; about .36 for the 5.56 gr bullet vs ~.28 for the 7.62mm bullet. And it starts with 400 fps more velocity. So it maintains 2000 fps all the way out to 300+ yards, even from a 16" barrel.
This is important because Fackler and others have shown us that tissue is elastic and amazingly resilient to so-called hydrostatic shock forces. Projectiles impacting under 2000 fps rarely show much damage beyond the permanent wound cavity created by tissue actually physically displaced by the projectile.Handguns don't produce the velocity to destroy tissue through cavitation, so their wound channels are measured in fractions of an inch, usually slightly smaller than the expanded diameter of the projectile. Rifles do produce enough velocity to destroy tissue through cavitation, which is why a wound channel from a rifle can be several inches in diameter. But it is highly dependent on velocity.
Your typical 7.62x39 round is essentially a .31 caliber handgun round by the time it reaches 150 yards. The bullet may or may not expand much below 1800 fps or so and even if it does expand, damage in the temporary stretch cavity is going to be non-existent. Meanwhile, the 5.56 loaded with a 75-77 gr OTM can expect to retain more velocity at 150 yards than the x39 has a the muzzle. An expanding 5.56 bullet impacting with enough velocity to cause cavitation damage is likely to create a wound channel much larger than the slower .31 caliber projectile.
The 77 gr OTM round was developed for US SOCOM on behest of some tip of the spear guys who wanted more range from their 5.56mm platforms. It has been used successfully in combat out to 600 yards and beyond. The Mk 262 Mod I is the most accurate ammunition ever adopted by our military and has proven to be very effective on humans. As a medium game round, I wouldn't hesitate to take any broadside shot I had out to 300 yards with that round, easily 3x the distance I would feel safe shooting an animal with any 7.62x39 load. The stubby Russian round just doesn't have the velocity to kill like a rifle beyond about 100 yards.