I have been looking into getting an AR-10 and have been going back and forth between a 308 and a 300 Ultra Mag.  But then I got to thinking about my M1A and what a great rifle it is.  That is when I put the two together.

If an AR-10 can shoot and 300 Ultra Mag why can't an M1A do the same thing?

Any one have an answer for that?  hinking.gif

In the temporary absence of someone who actually knows what they are talking about... lemme throw-out my totally uneducated $.02 worth on this issue.

Isn't the .308 sort of a short-action round? And would the receiver even be able to deal with the length of the .300 ultramag case properly? And what about the whole gas-piston timing thing? I realize that they can tune an AR platform for a different round, but I dunno... it just seems like maybe the M14 receiver might not be as adaptable to a variety of different calibers as the AR receiver. I'm not claiming to be any kind of expert here, so please forgive me if I'm totally wet on this deal. Just throwing-out some things for ponderance...

The M14/M1A receiver length is too short for the 300 UM. Charles the Gunsmith.  

You would destroy the gas system for one thing, not to metion the action is too short.  The main question is why would you want a 300 mag gas gun?

Want a 300 get a bolt gun.

maybe hes talking about the short action ultra mags?

you wouldn't be able to open the bolt face enough