OK, I will preface my remarks by saying that I not much of an expert on guns the way so many others are on this site. But from what I learned and what I know from direct experience from tools (where I do have a good background), it seems to me that not every rifle is best for all situations. In some situations the M16/M4 is better and in some situations the larger round 7.62 is better. It all depends on the terrain and the situation. So there will never be the perfect rifle for all situations, just like there isn’t a perfect universal tool.
Ah, the reasonable man. I agree with you 100%.
Like you, I'm not a ballistics expert. And like you, I think there are other things to consider besides pure wound dynamics.
Trying to boil it all down to the downrange performance of a particular cartridge on a shot-for-shot basis begins with the assumption that the bullet hits its mark.
IIRC, somewhere there was research which said that only about 1-in-10 or 1-in-12 small arms rounds fired in combat is actually aimed. The rest are generally flung downrange with a 'to-whom-it-may-concern' note attached, or while trying to ratchet up the flinch factor. The superior performance of elite units depends less upon the innate skill of the soldier, than it does upon the fact that they actually aim more than their regular counterparts.
When you consider the lack of actual aiming, then other factors come into play in selecting a combat round, factors which would include logistics (the bulk transport weight of the rifle and the round) and induced fatigue (carrying ammunition and weapon, and pounding from the recoil).
So the M4 and 5.56 become more likely candidates for issue, when the peripheral factors are considered.
I give you the socket wrench of the shooting world, the FN SCAR Rifle that is in use by our special forces.
Exactly right, but that won't prevent this longstanding argument from continuing NOR will it prevent the .mil brass from wasting millions of dollars and many lives persuing a one-size-fits-all solution to small arms procurement.
The fully-incomplete list:
A heavy 7.62 x 51 rifle with a 20 round box and 24" barrel will not be a good choice for room-to-room ops.
The 5.56 round may gain you fire superiority in terms of volume, but what the enemy once only used for concealment is now COVER.
The pain in the butt of getting your M16 in and out of rooms and vehicles is payment for the fact that the extra 6" of barrel helped make the round work as advertised.
An M4 is not the appropriate tool to take out the jihadi 1200M away on the next Afghan mountaintop.
You WILL lose muzzle velocity on a 5.56 round when you cut your 20" M16 barrel down to a 14.5" M4 barrel.
When you tighten up the twist on that M4 to get more downrange accuracy on your new, slower 5.56 round, the bullet will now have even more tendancy to punch through and through and not get the yaw and frag that the design once yielded.
When you move to a round designed to defeat Soviet body armor, it may not work as well on unarmored 110lb Somalis.
If you switch from a 5.56 to a 7.62, 6.5, or 6.8, your 200+ round combat loadout WILL weigh more.
If you switch to a "green", lead-free bullet, don't be surprised later on when you find an unpleasant trade-off for your environmentally misguided decision.
Pick your poison. Then bring along a squad designated marksman with a scoped .308. Don't forget the Forward Air controller who's really good with a radio either.
If they’re comparing the 7.62x39 round to the 5.56 round straight up, the larger bullet is not “better.” The 7.62 bullet is larger, but it’s much slower. It’s around 2900 feet per second compared to 2100 fps for the AK-47 round.