AR15 Upper Question

[mugsie]

I've seen AR15 uppers for 6.5mm, 6.8mm and 50 beuwolf. Are these directly interchangable with an AR15 lower? What about magazines, will they all fit in the lower mag well? I'm thinking about trying out another caliber and was wondering if any of you had tried these combinations and what your results were. I know 7.62 x 39 is also another option as well. Any problems with any of them or just stick with the vanilla 5.56?
Thanks....

 

[TX1911fan]

All of those uppers will fit on a standard lower. I don't know if you can use a .223 magazine though.

 

[alucard0822]

the uppers you named snap right in, but most of the alternative chamberings use a different mag. some uppers in larger calibers (300 win mag up to 50 BMG) are single shot, and some in 9mm use a mag adapter with either proprietary, or common SMG mags.

 

[SpeedAKL]

You'll need to get new magazines for the .50 Beowulf. 7.62x39 would require a different lower IIRC...

...also, 6.5 Grendel and 6.8SPC require new mags