[TexasARGunna]

Right guys, looking for some clarification here.

What caliber uppers can "drop in" to a complete AR upper, allowing to switch between a .223 complete upper and "X" caliber conplete upper with LITTLE to NO modification to the lower.

Also, which of these calibers allows use of normal .223 mags?

Please no useless comments like "why waste the money on multiple uppers". It's my $, and works best with my situation


Regards,
Adam

[jeepejeep]

There are a lot of calibers for the AR. What comes to mind are these:
450 Bushmaster, 450 SOCOM, 50 Beowulf, 6.8SPC, .20 Tactical, .204 Ruger, 6.5 Grendel.
As far as I know, the bigger calibers to need the follower to be replaced or a different mag.
I have the 450 Bushmaster and love it.

[TexasARGunna]

All of those mentioned will work fine with a normal lower? I know you need a different lower to run .308 correct?

[jeepejeep]

Yes all these work on the standard 223 based lower. The AR10 is necessary for the .308 and some others. I'm not real familiar with the AR10.

[mjkeat]

Add .300BLK, .22lr, 7.62x39,

.300BLK (.308 bullet in a 5.56 case) uses the same parts as the 5.56 except the barrel including mags, receivers, and BCG.

[fsted2a]

Originally Posted by mjkeat

Add .300BLK, .22lr, 7.62x39,

.300BLK (.308 bullet in a 5.56 case) uses the same parts as the 5.56 except the barrel including mags, receivers, and BCG.

Add .40 S&W, 9mm, .25, and various other pistol rounds. Most of them you can just change out the barrel and bolt. I think GSE has several pistol round choices you can get, but you have to buy a whole upper from them.

Caveat- the .22 doesn't have enough gas to push the BCG through the buffer, so you have to get a special blowback BCG with built in buffer. Upside is you don't have to change barrels, as a .223 is just a .22 extra magnum, and the rounds will fire the same, although some setups obviously work better than others.