Mag and feeding problems

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Re: Mag and feeding problems

Postby GB30 » Sat Feb 09, 2019 6:58 pm

I'm new to the AR15 format so forgive me if I don't know or use correct technical language

I have a new BM450, overall I like the rifle but I'm having feed issues. When I purchashed the rifle I also ordered one spare mag from BM.

1st issue was was mainly with the extra mag, round would not go all the way to battery, or sometmes get stuck in the mag. could only get 4 rounds in mag, fifth round would need to be forced in. Found that the extra mag had another follower in the bottom for a spacer - looked like follower for a 308??? Sent spare mag back to bushmaster for replacement - both mags are the same now.

Current issue - With the bolt locked back if I insert a new mag the round most often pops out of mag. If I close the bolt before inserting the mag the round stays in the mag. But I still get intermitent stovepipes or double feeds.

Observations: I found that if I tap the mag so all the rounds go forward I can load the mag with the bolt locked back and it seems to cut down on misfeeds. I think that the rounds get shoved back do to the shock of firing the rifle so just getting them all forward to begin with isn't a good fix.

I found that the tab that locks the bolt back after last round is contacting (hanging over) the case of the round (see photos) and can cause it to tilt up or pop out altogether. I can see where this might cause misfeeds as the following round could actually be out of the feed lips as the bolt come back to battery???

The rounds do not seem to be sticking out the back of the mag. Also, no modifications have be done to the magazines or rifle.

Anyone had any issues like this?

thanks in advance, Gary
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Re: Mag and feeding problems

Postby Bmt85 » Thu Feb 14, 2019 2:34 pm

I haven't had to deal with that, yet, but have heard of it. Something is out if spec. I would take all other AR mags, doesn't matter the caliber, and check them. If the bolt catch looks like its protruding into other mags, I would trim it. If it's only protruding into that mag, then maybe trim it a little, or just don't run that mag.
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Re: Mag and feeding problems

Postby Hoot » Thu Feb 14, 2019 7:23 pm

If the round rises into position with enough nose up tilt, the rim gets tilted backward to where it can snag the BHO latch.
its a symptom not a cause. Try cutting a few turns off the bottom of the mag spring and/or squeezing the mag lips together a little. Most double stack mags have way too much spring force for a single stack application.

In Theory, there is no difference between theory and practice. In Practice, there is.
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