ar lowers- upper compatiblity

[flinter4deer]

I have an Superior Arms AR lower. would like to build A4 varmint.Should i stay with a Superior upper or is there a better upper rig? are most AR uppers and lowers compatible?

 

[Walkalong]

Any in mil-spec upper will fit on an in mil-spec lower, pretty much. Which uppers are best is a wide open debate. Many good ones.

 

[taliv]

and even almost all non-mil-spec uppers will fit on almost all lowers. for instance, all the cool monolithic uppers and billet uppers, etc.

and if i were building a varmint upper, i'd definitely consider a billet. get the stiffest thing you can find

 

[flinter4deer]

Thanks,guys,any more ideas for such a setup?optics,barrels,good loads for fox, 'yotes and hogs?