Originally Posted by
jmoore
Pretty much all of the cartridge guidance is by way of the magazine feed lips on the M14 type mags. About the only contact with the receiver body is up front. So, what you see on the raw casting is pretty much it, except maybe a bit of polishing of the short feed ramps just behind the locking recess. I've found that many M14 mags will work "as is", 5, 10, or 20 rounders. But used mags may need some minor widening of the feed lips at the rear particularly or the bolt will ride over the round without picking it up. Even "tweaked" they still wwork in M14 type rifles, so it's the M85 that's more "sensitive".