ar 15 lowers and uppers
 

I was told that you can take a ar15 lowers .223, and add a upper that is 7.62 and have a 7.62 ar15. i called bushmaster and they said that was true. My question is can you take any cal upper and do the same.

RE: ar 15 lowers and uppers
 

Yes. any AR-15 uppers will fit an AR-15 lower- but you need the proper magazine in some circumstances. There are even single shot .50 BMG uppers available now:D

RE: ar 15 lowers and uppers
 

Depending on what you mean by 7.62. You can't take a standard AR15 lower (5.56) and put a 7.62x51 (308) upper on it.

If you want a 308 you need an AR10 lower.

With the standard 5.56 lower you can do a 7.62x39, 50 Beouwolf, 6.8SPC, and a load of other cartridges that are the same length or shorter than a 5.56 cartridge.

Go to ar15.com and you'll learn alot over there.