Black Rifle question

[GhostKnight]

This is both a game and real life question.

I'm looking at buying a Rock River AR15. I'd like multiple calibers - 308, 223, 458, 6.8mm, and 9mm. Will the same lower assembly accept all of the above upper assemblies despite the different calibers?

[Jefffar]

As a general rule, yes.

[BigLEE]

The .223, 6.8 & .458 uppers should all work with the same lower as their magazines all have the same outer dimensions, and you can get a 9mm adapter for a AR15 lower. But a .308 magazine will not fit on a standard ar15 lower. You might still be able to mount a .308 upper on a .223 lower, but your rifle would be single shot.

[Rockwolf66]

Lee's right about a .308 upper not fitting a .223 lower. The .308 upper is longer slightly in order to fit the 6mm longer .308 round. Thus if you have looked into building your own Armalite, you realize that various parts will not fit right between an AR-10 upper and an AR-15 lower.

[GhostKnight]

Rock River only sells 1 lower though. I'm still digging as to a contact that I can email them directly.

Could a larger 308 receiver also handle larger loads such as a 300 mag, 338, or 375? Hrm...

[GreenGhost]

This is both a game and real life question.

I'm looking at buying a Rock River AR15. I'd like multiple calibers - 308, 223, 458, 6.8mm, and 9mm. Will the same lower assembly accept all of the above upper assemblies despite the different calibers?

A buddy here at work said that another option would be to go with Cobb Manufacturing. The magazine well can be changed out without having to change the lower receiver. He said that he isn't sure about civilian sells, but you can always check out their website to see whether it's something that'll work for you or not.

[BigLEE]

Rock River only sells 1 lower though. I'm still digging as to a contact that I can email them directly.

Could a larger 308 receiver also handle larger loads such as a 300 mag, 338, or 375? Hrm...

They have a forum over at ar15.com, http://www.ar15.com/forums/forum.html?b=2&f=38
Or call them at 1-866-980-ROCK.

As to the second question, I've heard of AR-10 being rechambered to .300 Winchester Short Magnum, but the other cartridges you mentioned are quite a bit longer than the 7.62x51 cartridge, so it best it'd be a single shot rifle. For the amount of money you'd spend you might as well just buy a decent bolt-action.