According to the info I pasted below, the AR-10 can use a modified m14 mag, and the LR-308 can use some AR-10 mags, so then is it possible to use a modified M14 mag in an LR-308? Can someone with an LR-308 mag and an m14 mag compare and see if this might be possible? I'm asking because I plan on purchasing an LR-308 soon and magazines seem to be in short supply...
From the DPMS FAQ:
Do other magazines work in the LR-308 line of rifles?
Yes, the original AR-10 Stoner waffle 20 round magazines and the Knights Armament SR-25™ 10 & 20 round magazines will also work.
And from Technical Notes on the AR10, and Comparison to the SR25
MAGAZINE: The AR-10 magazine is based on the magazine of the M14 Rifle. The M-14 magazine is well proven and available in large numbers. It is both stronger and more reliable than that of early AR-10 and similar magazines. It is made in 10 round capacity.
The AR-10B magazine does not bear a latch plate on the rear surface like that of the M-14 magazine. The lower receiver, however, has a clearance cut up the back of the magazine well to allow insertion of an M-14 magazine. A 20 round M-14 magazine can therefore be modified to function perfectly in the AR-10. This modification requires changes to the feed lips cutting a magazine catch opening cutting a slot down the back of the magazine replacement of the follower with a new follower addition of a bolt catch trip and spring a slight change in the follower spring.
The most unique aspect of the ArmaLite magazine is the follower. A top surface similar to that of the M16 magazine has been combined with a form suited to the M-14 magazine box. A patented spring-loaded plunger has been installed in the follower. When the follower rises to the top of the magazine box, this plunger pops into the track at the rear of the magazine well and trips the bolt catch, thus holding the bolt carrier assembly to the rear.
The magazine will continue to function in the M-14 rifle, but will not trip the M-14 bolt catch unless the AR-10 follower is replaced with the M-14 follower. The latch plate at the rear of the magazine (which engages the M-14 magazine catch) may be sufficiently weakened by removal of its upper half that it breaks off, rendering the magazine usable only in the AR-10.