300BO fail to pick up next rond

[popper]

Just recently started having this problem. LBOE works fine but carrier hangs on finger of LB lug before mag is empty. It does not catch on the back of the lug as normal. Works OK releasing the bolt. Rifle lower, carbine upper. Turned up the gas and still happens, mostly on cast but often on super jacketed. Anybody know what that little 'finger' on the lug is supposed to do? 308 doesn't have it.

[petroid]

The "finger" on the bolt catch is pushed up by the magazine follower when the mag is empty, raising the catch to prevent the bolt from closing. Make sure the catch moves freely and the spring is properly installed

[popper]

Carrier catches on the finger, not the catch. Maybe mag spring is too strong, next round moves forward? Catch moves freely. Can't 'look' at it when fired but when releasing bolt (empty mag) it catches on the finger. Weak recoil spring? Just started happening after a year or so.

[petroid]

158137
When you referred to the "finger" I assumed you meant the extension that hangs into the magwell. when the magazine is empty, this extension is pushed up by the follower, pivoting the bolt catch up which (after the bolt carrier travels rearward) catches the bolt carrier so that it locks open. there is a spring under the bolt catch that keeps it "down" until pushed up by the empty magazine. You may have a weak bolt catch spring or an issue with your magazines and how they lock in place. If they are seated too deep, they will push the catch up enough to grab the bolt carrier. Or the followers could be the issue

[Vann]

If this is a new gun or you just changed the buffer and/or tube. I have run into out of spec buffer tubes and buffers. This will cause it to short stroke and the bolt will lock back but not in the right position.

[petroid]

Detach the lower from the gun. Insert a loaded mag. Verify that the catch is still down. Insert empty mag. Verify that the catch is now up.

[popper]

158375
White line I drew is where the front of the BCG hangs. Same mags (40WT), spring is good. I'm assuming the follower is coming up too high. I sort of worked around it when at the range, I'll investigate more. I'm surprised the BCG doesn't have enough force to push the follower down or recoil is pushing rounds forward in the mag enough to allow the finger to catch. Thanks.

[petroid]

If the bcg catches on that finger then it means the catch is in the up position. That could be due to a weak bolt catch spring or it could be pushed up by a round in the magazine if they ride too far back. Does it only happen with those magazines?

[mcdaniel.mac]

158375
White line I drew is where the front of the BCG hangs. Same mags (40WT), spring is good. I'm assuming the follower is coming up too high. I sort of worked around it when at the range, I'll investigate more. I'm surprised the BCG doesn't have enough force to push the follower down or recoil is pushing rounds forward in the mag enough to allow the finger to catch. Thanks.
I assume 40WT means magazines modified by Wilson for that caliber? Have you tried with standard mags? I find that even .300 Whisper will reliably feed from 20rd straight mags like the older Pmag and the Colt 20rd mags. I don't know what Wilson does, but is it possible those mods are causing the issue?

[popper]

Couldn't get the Lancer 40WT to do it today but the follower is ~0.020 higher than the follower on gen3 pmag. Appears the back anti-tilt follower leg on the lancer is too short so the follower tilts.
158439
Spring bending time.

[petroid]

So the follower is tilting and riding too high and picking up on the bolt catch? Hope you figured it out and can get it sorted.

[mcdaniel.mac]

Couldn't get the Lancer 40WT to do it today but the follower is ~0.020 higher than the follower on gen3 pmag. Appears the back anti-tilt follower leg on the lancer is too short so the follower tilts.
158439
Spring bending time.
That makes sense, Blackout is almost a straight wall case.

I don't suppose I could convince you that it's worth just buying a couple standard AR mags instead?

[popper]

I have other mags, pmag, etc. but they don't feed FN or RN very well. Pmag has a taper at the front of the mag that causes problems even when the rib is ground down. The 40WT doesn't. Followers don't interchange so I'll tinker with the follower. Receiver doesn't have FA so can't just tap it home. Thanks for the replies, it started happening after ~ 100 rnds and just caught me by surprise.