As has been mentioned above, and to simply drive the point home, you can't mix and match AR10 upper and lowers with AR15 uppers and lowers. The .243, .260, and .308 uppers will have to be married with AR10 lowers. Many other calibers are available that will work with the AR15 lower such as but not limited to the .223, .204, 223 wssm, .243 wssm., .25 wssm, 6.5 grendal, etc.,
The AR10's will be heavierbut will still have more felt recoil than the smaller calibers in the AR15's.