bring on the cokc jokes in 3.....2.........1!

seriously though, does anyone make an upper receiver that barrel extension area could be reamed out, and at the same time have female threads, so a fatter diameter barrel extension could be mounted?  i wana say aero precision has that monolithic thing but not sure what threads like

I'm not seeing how a female thread would allow a larger extension? also how would you get every extension exactly the same so headspace wouldn't be an issue?

but to answer your question the freedom group (aka Remington, dpms, bushmaster ect.... have made a hybrid upper if want to call it that for the now defunct 30 Remington AR and the 450 bushmaster that basically uses a .308 extension and bolt in a modified carrier and beefed up upper receiver.

so point of female threads be just the way ive seen it done on some other things... thats prob not necessary though...  im gonna try callin remington/bushmastr/acme gun co tomorrow and see if they sell their stripped upper

If you have the capability to design, and machine a new wider/stronger barrel extension, do you not also have the capability to design and machine a new billet upper receiver to accommodate it?

probably be cheaper to just buy a 450 bushmaster upper complete and pull the barrel out of the extension and that way you have everything you need, the bigger receiver, bolt and carrier.

good point, somewhere online they way cheaper than midwayusa, think its buds....