[The Reaper]

I am not a graduate of Thermodynamics, but the brass case heating up would seem to me to some degree to act as a heat sink removing heat from the chamber.

Obviously, at some point you reach sufficient heat for a cook-off, and then all bets are off.

How many people need a rifle capable of 400 meter plus accuracy when the Army trains out to a maximum of 300 meters on a pop-up target?

How often do we get an opportunity much less a requirement for a squad to engage targets at more than 300 meters?

Has anyone taken their unit with their assigned weapons and effective long range ammo out to a real rifle range, out to 1,000 meters and taught them how to engage targets at longer ranges?

Why is the military always looking for a mechanical change, or a magic bullet to replace adequate training? The three round burst mechanism is a prime example of this. Doubling the time on BRM and allowing shooters with potential to attend advanced rifle marksmanship training would seem to me to be a much cheaper solution than replacing every rifle, light machine gun, and round in the inventory. But that is just my opinion.

The environment would seem to dictate the long range requirement and the interchangeability of the AR would seem to me to be ideal for maximum flexibility. Most of the team members I have known have used their M-4s a lot more up close or inside buildings rather than at extended ranges. Situations calling for 600 meter plus engagements are better assigned to a 7.62 NATO weapon for the terminal ballistics. A squad or an ODA could have an M-240 or two, a couple of M-249 SAWs, several M-4s, and a couple of designated marksmen with 7.62 long-range rifles while requiring only two different mags, two different belts, and two types/calibers of ammo, and that would seem to me to have them well-equipped for anything from muzzle to 800 meters or better. Any addition of intermediate calibers or SMGs could result in a half-dozen different calibers and as many feeding devices, most of which are not interchangeable.

The best solution I can see is for the units to have both 5.56 and 7.62 NATO caliber weapons in the arms room, allowing a unit to conduct their own threat analysis and deploy with whichever caliber (of the two) mix the units feel is optimal. If they want a longer range designated marksman with a reduced ammo load, so be it.

Allowing smaller-statured, lower-testosterone soldiers with lesser-upper body strength would seem to me to be an argument against allowing them into combat arms MOSs, but what do I know? How will they cope with the heavier weapon and ammo, and consequent reduced basic load? Will their male counterparts have to carry more to make up for them?

One of the major advantages of the AR series weapons is the ability (within the same action length) to go from a 7" to a 20" barrel merely by swapping out the uppers. You can configure as a submachine gun, a carbine, a DMR, or a full length rifle by just swapping uppers. All can use the same ammo and mags.

Having an arms room full of U.S. and foreign weapons is all well and good, but being able to borrow a mag from any other squad member when running low in a firefight has a certain appeal to me. Having a mix of three or more calibers and feeding devices among a handful of troops would seem to me to be a significant concern. 5.56 in the Mk 262 loading can be effective well beyond the range of most shooters. IMHO, there is little if any range gap between the 5.56 and 7.62 NATO, as long as the proper loads are selected.

If we have to go through this all over again, I would like to see the comparisons include the 5.56 Mk 262 Mod 1 rounds and a good 6.5 Grendel load.

Personally, I do not see the short, 5.56mm based 6mms/.243s representing significant improvement over the 5.56 and 7.62 NATO.

The .300 AAC Blackout has a niche for subsonic operation, and works as well as an AK at shorter ranges, but certainly has limited long range ability.

The long 6.5/.260 calibers such as the .260 Rem and .6.5 Creedmore are great performers in external ballistics, but require a change to a .308 sized action. The shorter 6.5 rounds, like the Grendel, are interesting, but until we are ready to replace the 5.56 in all applications, not really feasible for a couple of rifles per squad. I am not sure that the limited case capacity will allow the outstanding 6.5 projo to reach its full ballistic potential.

The 7mm/.284 rounds are again, going to require a larger weapon with a 7.62 NATO sized action.

Perhaps the real issue here is the movement of the Army toward "green", lead-free ammunition (like the M855A1) that appears to have been selected for environmental/political reasons and seems to be less effective than the rounds that proceeded it. When you place wacky environmental concerns over efficacy and our soldiers' lives, you have these problems.

Pardon my wandering, multiple issues occurred to me as I was writing this.

As always, my .02, YMMV.

TR