Well... I finally got to zing some flextips down range today and although I'm very pleased with all the factory groupings (sub MOA) at 50yds from a sack of corn; I had some feeding "issues" with the factory & BM modified GI mags. Here goes...
First 5rds from factory mag; starting with an open bolt, went fine but the bolt didn't lock open on the last shot. When charger handle was pulled all the way back it locked against the empty mag follower like it should have done when the last shot was fired... dumped the mag and duly noted
Next, I reloaded the gun(closed bolt) with a BM modified GI mag with 10rds. It went home and locked into the mag well with no issues. When the charger handle was pulled all the way back and released, it picked up the first round and went home just short of "fully" closed. Bumped forward assist to close the bolt. Fired first 5rds... all 5 needed forward assist "bumped" to complete the cycle. Last 5rds functioned flawlessly; BUT, the bolt didn't lock open on the last round AGAIN. Dumped the mag. Reloaded, released the bolt and needed forward assist again for the first 5rds. The next two BM modified GI mags (10rds each) did the exact same thing!!! ...as well as the factory mag. Bolt never locked open on last round with any of the mags. Only when drawn back by hand did it lock open.
My son (brass catcher/spotter) noticed almost immediately that most of the ejected brass was scattered aimlessly across the ground with some very lazy ejects only traveling 2 or 3ft from the gun; some showing signs of sooting at the mouth, but fully compressed primers on all rounds... again, sub MOA groupings at 50yds! He suspected the ammo We were shooting between rain showers so I never setup the Chrony... but again; sub MOA at 50yds. The extreme spread couldn't have been that "extreme"!
That's when I thought about the M16 heavy buffer! He wanted to swap buffers from one of his AR's (5.56) that he brought along, but I was satisfied with the scope, gun & load combo so I declined. We checked the bolt travel and it is fine. The bolt has several .01's travel past the lock before the bumper hits the back of the spring tube
Any ideas?