If you were the boss, what would you have the AR chambered in? I'm sure there are a lot of 5.56 and 7.62 fans, but what about something different?
Feel free to elaborate as to purpose (e.g., M-4 in .375 RUM for starting fires.)
I'd like to see what the '06 case, cut down to 1.76" and necked to .264", loaded with 100 gr ball would do out to 300m.
I have a hunch it would be pretty darn in-between, in terms of cartridge weight/volume, muzzle energy, caliber and velocity, but better SD and BC than either.
Assuming something close to 3000 fps, that is.

I want to play with the bigger brother AR-10 thats coming out in the 300wsm, now that is a hog busting rifle

Call me square, but the good old 223 Remington works fine up to about 700 or 800 yards with the 80 grain VLD bullets, and up to 1000 with the 90 grain.

That assumes you have a barrel with enough twist to stabilize. 1 in 8 will do for the 80s and 1 in 7 will do for the 90s.

Orion1, have you been having success with the 7twist/90JLK's? We've been finding a 6.5 twist has been necessary to reliably stabilize the 90's.

How hard are you pushing them to 1000yds? 20"bbl?

Personally I'd like to see the 5.56 bullet replaced with an 85 grain 6mm bullet, same case, etc.
Jim

I agree that the 223 is pretty hard to beat. I don't think that 6mm would be enough of a step up to make a big difference in killing power. I would have something scaled up to .25 with a .400" head size launching a 105gr bullet to at least 2900fps. Same case length as a 223. Wonder if that would be possible?
One interesting one I heard was the .25 Remington loaded to modern pressures and maybe improved a little.

For those wanting an AR-10 in 300 WSM, SSK Industries is making that exact rifle. Armalite makes the AR-10 in .243 for the 6mm fan, and of course, there is the .458 SOCOM and the .50 Beowulf and many more. If you can think of it and is doable, I bet someone out there is making it.

BECoole, there's the .257 Kimber, the .222 Rem Mag necked to .257" and it's only .06" longer than the .223 Rem.
That, same cut down to 1.76", same of both necked to .264" - I'd love to see what these do with 100grs.

No one agrees on the ideal set of performance parameters for a general-purpose military round; some have more emphasis on caliber, some on bullet drop, some on terminal energy, some on cartridge weight/volume, still others have restraints based on rifle design (e.g., short-barrelled velocities).

How many rounds should you be able to carry, for how long/far? What's the maximum effective range needed (energy and/or caliber)?
Seems there are many who say the .223 isn't as strong a stopper as it should be, and many saying the .308 is way too bulky, too heavy recoil for select fire.

Am I leaving anything out?

Becoole
"Of course you are right. I've never heard of a good stopping rifle that troops didn't complain about the weight and I've never heard of a lightweight rifle that the troops didn't complain about the stopping power"

In these times, especially in all of the services except the Marines, the problem is marksmanship, range time.
The guy who can put two 22 RF into a one pound coffee can at 100 meters, verses a guy who can't put two 50 cal rounds into a 55 gal drum at the same distance????
Jim

arkypete,
the sad part is they fire about 20 full auto to get the 2 in the 55 gal drum.

I thought i'd answered this line before but my 2 cents is on an AR-10 with an AR-15 charging handle. If were scoping the rifle Savage or Remington bolt action in 7.62 or .300 Win Mag. Two tottally diferent rifles and uses.

I'd like to see them experiment with a 6.5 TCU concept, maybe try a 120 gr bullet of the same design as the current M855 ball. Of course velocity would be limited so it would be up to the powers that be to determine if the loss of velocity was worth the increase in mass and diameter.
I also heard the 5.56 doesn't do too bad with the heavier 75 gr MatchKings and such.
I would also like to see the military adopt the H&K G36 series, or some other AR-18 derevitive.

I know this will sound weird but how about one chambered in 250 savage with a fast twist barrel and a 100 to 115 grain boat tail bullet?

I think i would like to see one in .350 Rem Mag

I think it IS possible to design a military rifle/MG cartridge which combines effective hitting power with recoil light enough for full-auto fire from the shoulder.

This article analyses the subject of cartridges for assault rifles and suggests a range of possibilities in the 6 to 7mm range: http://www.quarry.nildram.co.uk/Assault.htm

Tony Williams: Military gun and ammunition website and discussion
forum

Muzzle, I was going to suggest a neck-up .22-250, an offspring of the .250 Savage. It would have about 1/3 more capacity than the 5.56.

The 45/70 & the 30/06 are the two best miltary rounds ever devised in mye eyes. The 6.5x55 also comes in at a close thrid. I reckon the 6.5x55 would have been a great choice also for an American Military cartridge.

AR-18 in .243 winchester or .260 reminton

what would this do.If I were to use a dpms 7.62x39 upper and ream the chamber[new dims rim dia.447/web dia .4460/at shoulder .4230 witha 28 degree shoulder,7.62x39 dims are rim.4470/web.4460/shoulder.3960 17degree shoulder would be better if I could get a .277 barrel

.257 Roberts.