I played with grendel in Pmag 30's a couple of weeks ago. Five or Ten rounds worked 100% in a box stock mag, though they looked like they would not. Fifteen failed miserably, with cartridges spewing out into a jam after the first shot.
Five rounds there was no noticeable bulge. Ten rounds you could tell it was a snugger fit in the mag well, but still was easily inserted, etc. Fifteen had noticeable bulge and had to be forced into the mag well.
Rifle had an AA 16" SS barrel/bolt, M4 ramps, AA upper receiver, LMT lower.
My read is that with a different follower it might work better, but the feed lips are clearly mis-shaped, and if carved would likely create retention problems.
That said, I've never had a problem with Grendel C-products mags, either 20 or 30 round type. Mine were made late 2008 to six months ago. Have had a few which were very snug in Sundevil billet receivers, but then again, so are most P-Mags.
Five rounds there was no noticeable bulge. Ten rounds you could tell it was a snugger fit in the mag well, but still was easily inserted, etc. Fifteen had noticeable bulge and had to be forced into the mag well.
Rifle had an AA 16" SS barrel/bolt, M4 ramps, AA upper receiver, LMT lower.
My read is that with a different follower it might work better, but the feed lips are clearly mis-shaped, and if carved would likely create retention problems.
That said, I've never had a problem with Grendel C-products mags, either 20 or 30 round type. Mine were made late 2008 to six months ago. Have had a few which were very snug in Sundevil billet receivers, but then again, so are most P-Mags.