Does anyone own or have shot an .450 Marlin in the AR-10 platform?  What are some specifics about the setup and who makes one?  I have seen that Accuracy Systems produces one, but how does the setup run with that caliber?

Good luck feeding a belted magnum.

Probably better off building a 458 WSM if you want more thump than a 458 socom.

Old post but read about half way down the page.
JN built one on a model 70 and is getting 2500+ with a 300 grainer out of a 16" barrel.

That said a 375 or 416 WSM would be a bit better I think
and a 20-22" barrel.

http://shootersforum.com/showthread.htm?t=6767

Yes, Accuracy Systems does, 450 Marlin
(scroll down 1/2-3/4 of the page)
I have one of their uppers in 6.5 WSM and they build a good upper.

that 450 marlin looks pretty cool but I think a 458 socom would be a better choice due to logistics and using a regular ar 15 platform . magazines will interchange as well as every other part except the bolt face needs to be opened up and the ejection port enlarged ,  on the other hand if it is what tweaks your iugs then buy it post some pics with a range report and make everybody pause and think do I need one of these things.