Quote Originally Posted by 2manymustangs View Post
List all of the chambers you know of the AR15 platform to be built in. I have .223, 300BLK, 7.62x39 and my buddy also has .243 (using EXTRA light bullets) in his collection. I have also seen 9mm and of course the blow back conversion bolt to shoot .22 LR.

Including your 6.8 that makes seven calibers...

Oh, I forgot, I sold all of mine yesterday at the gun show so I have none... I would love to get one to cycle properly with the conventional direct impingement set up in .17HMR...

Edit: Alexander Arms has a 17HMR upper but I dont know if it is a blowback bolt or if it uses D.I. gas action to cycle.

They also have a .50 Beowulf and 6.5 Grendel... Seems I recall someone making a custom lower to hold a .45ACP magazine so I looked that up and Olympic arms sells a barrel/kit for that...

That makes 11 calibers...
I've seen uppers chambered in .204 ruger. I'm tempted to do one of those with a heavy barrel and scope.