Quote Originally Posted by JaredP View Post
the only thing that is modified on that upper is a larger ejection port, much like the 50 beo and 458 socom ar15 uppers. some mfgs ejection ports are large enough by default.

the .532 bolt face in AR10s is also not uncommon, being used with the SAUM and WSM cases which are quite ubiquitous in ELR gas guns. so with the proper bolt, a 450 marlin would quite likely "drop in" a BCL or stag and work.

however, the point is that belts and semi-autos are not incompatible, so your explanation of "its belted" is not accurate.

EDIT: i just realized i had both a bcl102 and stag 10 receiver set on my desk, the ejection ports measure .555 and .575 on the BCL and stag respectively, so you likely wouldn't have an issue running 450 marlin.
Alright, buy the barrel and bolt and show me how’s it done.