What Caliber for the AR-15 ?

[wv109323]

I have a lower receiver for an AR-15 that I would like to build. I have two other ar-15s. One is in the heavy barrel A2 configuration and the other is a scoped flat top receiver with a 24 barrel. Both are in .223 Rem or 5.56 Nato. If you were going to build another rifle what caliber would you build ?
I would like to get as much energy as possible out of the ar-15 platform. I was looking at one of the WSSM and the 6.5 Grendel. I reload and for this application I would probably stay with j-bullets. your opinions

[RU shooter]

Dont know about the energy levels but ,I would go with the 300 blackout or whatever they call it,same as the 300 whisper but looser chamber in the neck If I understand it right. lots of bullet selection uses regular mags and brass to make it is laying around on the ground everywhere and I'm a 30 cal guy!

[johnly]

My 7.62x39mm AR-15 is a spectacular cast boolet shooter and the brass and ammo is cheap and easy to find.

John

[Otony]

6x45, nothing to mess with except for the barrel. Everything else interchanges insofar as parts are concerned, no modified or special magazines. Heck, you can even use .223 brass.

I read a Shot Show report that detailed info about a new (well, recycled) roundthat the sharps company is starting to use in their ARs. Before anyone jumps up about the Sharps name, it is apparently used by a company that makes AR uppers and lowers, no connection with Shiloh or C. Sharps.

Anyway, they have a .25x45, which appears to be an improved .223 necked up to .25 caliber. If I recall correctly, Kimber had somethig like that called the .257 Kimber back in the Clackamas days. Just a thought.....

[82nd airborne]

.257 Kimber is great, one of my favorites. If you want cheap firepower that minimizes non standard parts, just go with .300 BLK, or neck .223 up to any caliber you want.

Stay away from Olympic arms WSSM uppers with factory ammo.

There is also the 6.8spc II, that is good, the many varieties that can be done with the 7.62x29 as the parent case.
.338 spectre off of the 10mm mag, 30rem. or 6.8.

Then there are the plethora of big bores.

[johnly]

6x45, nothing to mess with except for the barrel. Everything else interchanges insofar as parts are concerned, no modified or special magazines. Heck, you can even use .223 brass.

I read a Shot Show report that detailed info about a new (well, recycled) roundthat the sharps company is starting to use in their ARs. Before anyone jumps up about the Sharps name, it is apparently used by a company that makes AR uppers and lowers, no connection with Shiloh or C. Sharps.

Anyway, they have a .25x45, which appears to be an improved .223 necked up to .25 caliber. If I recall correctly, Kimber had somethig like that called the .257 Kimber back in the Clackamas days. Just a thought.....

I'd be in for a 6x45 if the barrels became easily available again. Loosing 6 PPC brass out of my Olympic Arms upper gets spendy pretty quickly.

John

[82nd airborne]

I can make them in fairly good time. I shoot 6x45 and 7x45 alot. I think they should both be more popular than they are.

[huntinmo]

Since you mentioned that you are looking for energy, I can say that I really like shooting my 458 Socom. Not the cheapest ammo, but it does handle boolits just fine as long as they have a GC.

[Ickisrulz]

I have a lower receiver for an AR-15 that I would like to build. I have two other ar-15s. One is in the heavy barrel A2 configuration and the other is a scoped flat top receiver with a 24 barrel. Both are in .223 Rem or 5.56 Nato. If you were going to build another rifle what caliber would you build ?
I would like to get as much energy as possible out of the ar-15 platform. I was looking at one of the WSSM and the 6.5 Grendel. I reload and for this application I would probably stay with j-bullets. your opinions

"...as much energy as possible out of the ar-15 platform" would come from the big bores. .50 Beowulf and .458 SOCOM.

[BD]

I went with the .450 Bushmaster for practical reasons. Much cheaper to keep fed. It uses standard mags. It has better boolit selection, better brass availability and life, and it's a production round now with factory ammo and brass from both Hornady and Remington. BDC retical scopes that match the factory ballistics are available from both Nikon and Leupold. You can buy a 16" upper for under $550.

IMHO it's the .45acp of the black rifle world.

BD

[45r]

Since you already have stuff for the 6.5 grendel I'd get one of those,it would be quite accurate way out there.It's not so much how hard you hit sometimes but how well you place your shot.My next AR is going to be a 300whisper or 300BLK.It will do anything the 7.62x39 will do with easy to get brass and feed well with easy to get mags.My son likes hunting with my old mini-30 and it works real well on deer with speer 125's over AA1680.I figure the 300whisper would work just as well using 125 ballistic tips.

[crawfobj]

I have an upper in 300 whisper and I've been impressed so far. Still tweaking loads a bit.

My next one will be a big bore - either 450 bushmaster or 458 socom. Have GC molds for either diameter, so primary considerations will be bolt face, magazine compatibility and brass cost and availability. Don't anticipate using factory ammo at all.

I have a couple of projects ahead of this one, but it's on the list...

[82nd airborne]

I like .450 BM as well. I agree with BD's assesment, and he is one of the more knowledgable sources on said caliber.

[Landric]

I'd likely go with the .300 Blackout. As it happens, there is a 250 grain +/- GB going on right now for a boolit intended for the Blackout. If I can find some money I'm considering getting in on the buy, just in case I later decide I "need" a .300 Blackout rifle.

[Otony]

You can pick up 6x45 barrels nowadays. There are a few fellows making them. I bought mine about 6 or so months ago. Let me check for the outfit in Texas that is making them.

BTW, the owner of the company is the fellow who started up Springfield Armory as a commercial venture back in the late '70s.

[Ole]

450 Bushmaster!

[Artful]

Hmm so many AR choices besides 223, you asked "If you were going to build another rifle what caliber would you build ?"
When I did that it was 300 fireball aka 300 whisper ala 300 blackout - now with factory ammo availability and you can always convert 223. - advantages - 30 cal bullets from 70-250 grain cast or jacketed - only need to change barrel and it's back to 223 - works subsonic and supersonic and miserly on powder and easy on the rifle. You can set up with dual port barrel and with turn of a screw go from pistol to carbine gas tube length. (I'm still working on having dual gas ports) but of course this requires you like suppressed guns to really enjoy.

but you said "I would like to get as much energy as possible out of the ar-15 platform. I was looking at one of the WSSM and the 6.5 Grendel."
So it sounds like your looking for the long range not up close energy transfer so I can leave out the various .50, .45, .40, .35, .338 rounds -
I'd have to say I'd choose the 6.5 Grendel then, with right bullet you can match 308 at 1000 yrds in energy. And it betters the 6.8 SPC and other possible choices.

[82nd airborne]

Black hills is making 6x45 factory ammo now too, which will help resale value, if you ever decide to sell it. It is a great deer round.

[Moonie]

Hmm so many AR choices besides 223, you asked "If you were going to build another rifle what caliber would you build ?"
When I did that it was 300 fireball aka 300 whisper ala 300 blackout - now with factory ammo availability and you can always convert 223. - advantages - 30 cal bullets from 70-250 grain cast or jacketed - only need to change barrel and it's back to 223 - works subsonic and supersonic and miserly on powder and easy on the rifle. You can set up with dual port barrel and with turn of a screw go from pistol to carbine gas tube length. (I'm still working on having dual gas ports) but of course this requires you like suppressed guns to really enjoy.

but you said "I would like to get as much energy as possible out of the ar-15 platform. I was looking at one of the WSSM and the 6.5 Grendel."
So it sounds like your looking for the long range not up close energy transfer so I can leave out the various .50, .45, .40, .35, .338 rounds -
I'd have to say I'd choose the 6.5 Grendel then, with right bullet you can match 308 at 1000 yrds in energy. And it betters the 6.8 SPC and other possible choices.

Actually if you compare Spec II 6.8 ballistics the two are virtually identical and the 6.8 doesn't suffer from the broken bolt issues that the 6.5 Grendel does.

In hunting terms realistically either one is a good sub 400yard gun for deer size critters.

Yes, I have a Spec II 6.8. If I were to get another upper I'd probably opt for something 35 caliber, just seems right to me for a cast boolit slinger, 450BM would be a good choice as well.

[DCM]

OK maximum energy with j bullets, comercialy available. That would be the 300 OSSM from Olympic Arms. Next choice would be the 25 WSSM from Oly or D-tec. The 6.5 Grendel would be a good choice but doesn't come close to the power of the first 2.