Mag and feeding problems

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Re: Mag and feeding problems

Postby Texas Sheepdawg » Thu Feb 13, 2014 2:55 pm

My factory mag has that little steel plate in it.
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Re: Mag and feeding problems

Postby Hoot » Thu Feb 13, 2014 6:06 pm

Texas Sheepdawg wrote:My factory mag has that little steel plate in it.


I can't speak for current production, but for a few years each factory mag had two of those stamped steel tabs inside below the lips to form a set of centering shims, to encourage the bullets to sit in the exact center of the stack before rising into position to be stripped. From the results I've gotten from aftermarket bodies without those shims, they were not really needed. The slight dish of the follower top accomplished that. Perhaps the additional help was needed due to the excessive spring tension they didn't need, squishing the cartridges until they began to stagger. :roll:

The shame of that part of the design was the wimpy spot weld that secured the shims to the body. Oh well, if you didn't read the linked thread, Bushmaster made good and sent me another mag free of charge. I harvested the follower from the defective one to make another mag from an AR Stoner mag 20 rounder I had.

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Re: Mag and feeding problems

Postby dec » Thu Feb 13, 2014 6:24 pm

They still have the tabs inside the mag just below the feed lips.
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Re: Mag and feeding problems

Postby Sesshoku » Thu Feb 13, 2014 10:31 pm

Second day at the range was a lot closer to success. I did as DEC suggested and cut my mag springs and opened the mag lips. I also followed Hoot's advice and polished the mag lips and feed ramp. The result is every round stripped off the mag and fed into the chamber without fail, and I only had to use the forward assist once. I also got my Nikon scope reseated and fairly dialed in. So I'm gonna say two of my three problems are pretty much fixed.

I still had ejection problems. I had just about one stovepiped casing per group. I'm not sure what's causing that. My bolt is able to travel far enough back as it doesn't seem that the buffer is hitting any screw as was mentioned in a previous post. Something else is at work here. I can lock the bolt back with no problems. So, I still have to diagnose the brass ejection problems, but I was much happier with my range session today. Thanks for the advice everyone.
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Re: Mag and feeding problems

Postby Texas Sheepdawg » Sat Feb 15, 2014 12:09 am

When in the shot sequence was it stove piping? First shot? Last shot? Second to last shot? Somewhere in the middle?
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Re: Mag and feeding problems

Postby Sesshoku » Sat Feb 15, 2014 8:14 am

It generally happens on the second shot. A couple of times it happened on the last shot, but then it didn't necessarily stovepipe, it just didn't eject. It just stayed there on top of the empty mag.

When field stripped, I have pushed that ejector pin in to make sure it moves, and I've also made sure the extractor that I believe grips the case rim moves and both seem to function in regards to that. I've disassembled the BCG decreased, cleaned and lubed a few times now. Admittedly, I don't know enough yet about the function and timing of the system yet to make an educated guess as to why it is doing this.

When I was researching the .458 SOCOM before making the decision to go with the .450 BM, I know that Rock River shipped a second spring with the .458 upper, presumably to swap out in place of the standard .223 system spring. I wonder if not having a different spring has anything to do with it.
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Re: Mag and feeding problems

Postby Sesshoku » Sat Feb 15, 2014 8:16 am

I should also mention that out of 40 shots fired that day, mainly shot in three-round groups from my factory 5-round mags, the stovepipes/ejection failures happened 8 times.
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Re: Mag and feeding problems

Postby Texas Sheepdawg » Sat Feb 15, 2014 8:39 am

It generally happens on the second shot. A couple of times it happened on the last shot, but then it didn't necessarily stovepipe, it just didn't eject. It just stayed there on top of the empty mag.

Mine does that occasionally.
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Re: Mag and feeding problems

Postby Sesshoku » Sat Feb 15, 2014 8:53 am

I just read through this thread: viewtopic.php?f=2&t=10673&hilit=Stovepipe&start=50

It appears that I might want to check into the fixes listed there. I guess the bottom line is I shouldn't worry too much about it right now being it's a new rifle with only 60 rounds fired through it. I've hand cycled the action about 300 times to help the "break-in" process.

The good news is with the help of this forum and DEC, a buddy of mine, I'm now able to load up a magazine, pop it in and start shooting. When I first got the upper, that wasn't the case. I won't say I wasn't a little nervous after dropping $1k+ on a new rifle (and the ensuing marital arguments that ensued) and the thing not working at all out of the box. I've got a hog hunt coming up in a few weeks, and I expedited my upper purchase to coordinate with that. So, I guess I'm a little anxious about making everything work before then.

Thanks again for everybody's help. This is the best firearms/hunting forum I've ever been involved with in terms of available information and guys willing to help.

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Re: Mag and feeding problems

Postby Texas Sheepdawg » Sat Feb 15, 2014 9:27 am

Take out your buffer and look at the back side of it
Where the pad is.


image.jpg
#1 buffer
image.jpg (49.52 KiB) Viewed 23285 times


Using a pretty intense light will reveal a stamp if the
Screw is hitting the buffer pad.

image.jpg
#2 Buffer pad
image.jpg (43.88 KiB) Viewed 23285 times


This was my buffer after it had been smacking a screw
That was about 3/16"-5/16" too long. The bolt wouldn't
even lock open.

image.jpg
#3 Buffer pad stamped by over length screw
image.jpg (40.66 KiB) Viewed 23285 times
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