450 BM mags

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Re: 450 BM mags

Postby Hoot » Sun Dec 17, 2017 4:25 pm

Jim in Houston wrote:...snip...There's a thread here somewhere that talks about the problem of having magazines with springs that are too strong. As I recall, if you have this situation, start cutting the spring at the bottom one coil at a time until the spring has just enough tension to get the last round in the magazine firmly against the feed lips on the magazine...snip...


That would be this thread. ;)

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Re: 450 BM mags

Postby giannid » Sun Dec 17, 2017 5:51 pm

You guys think cutting the spring is ok or should I replace it with a regular spring from a GI 20 round magazine. If you cut it I imagine the bottom of the spring won't be held in place by anything like it is on a new mag. The Bart magazine is stiff compared to my regular 20 round colt magazine. Provides a lot more tension than the regular colt. Have people had good luck with the factory bushmaster 450 mag? They're cheap so I figured maybe I'd try one.
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Re: 450 BM mags

Postby Hoot » Sun Dec 17, 2017 9:20 pm

giannid wrote:You guys think cutting the spring is ok or should I replace it with a regular spring from a GI 20 round magazine. If you cut it I imagine the bottom of the spring won't be held in place by anything like it is on a new mag. The Bart magazine is stiff compared to my regular 20 round colt magazine. Provides a lot more tension than the regular colt. Have people had good luck with the factory bushmaster 450 mag? They're cheap so I figured maybe I'd try one.


Cut the spring. Take a winding off at a time and reassess the resultant tension. You can form it like the original bottom with a strong set of needle nose pliers, but retaining it to the bottom is not necessary. Its all a matter of personal preference. I've told Brett this already but I'm no fan of the side tabs spot welded on just below the top of the mag. I understand what they do but I feel it is unnecessary for successful operation. We all have our opinions. IMHO, those tabs add resistance to the cartridges rising up into place and necessitate more spring tension to overcome the additional resistance. I squeezed mine as close to the mag walls as possible, then polished them and rubbed a little Renaissance wax into them to slicken them up.

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Re: 450 BM mags

Postby Avenger10 » Mon Dec 18, 2017 1:23 pm

Clipping off coils is a catch 22. When you clip off coils to make an upper function you run the risk of the bolt not locking back on an empty chamber.

We have never cut a coil to make an upper run with our mags. As Hoot pointed out our mags are stiff lipped. Sometimes they need to have the front edges tweeked up .010"-.020" to provide a better launch angle for the rounds when the magazine is at or near full capacity. Brownells sells a lip adjustment tool that every AR owner should own. Please try adjusting the feed lips before you cut anything. We have sold thousands of magazines since 2014 and have had no problems and we don't cut coils.

We have noticed that since people have started using more full capacity magazines this problem comes up once in a while. Properly adjusted lips will have the round sitting at an up angle and not parallel with the top of the magazine.

I'll bet dollars to doughnuts this is the issue.

Please follow up and let us know.

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Re: 450 BM mags

Postby giannid » Mon Dec 18, 2017 3:00 pm

Well my AR definitely doesn't like the Bartz mag as it functions much better with a colt 20 round magazine with a 450 follower I bought from ebay. Doesn't seem like the lips need any tuning as I checked them with a micrometer compared to the colt mag. My only guess is that it is the spring pressure. It has a lot.
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Re: 450 BM mags

Postby MOOSE EARS » Mon Dec 18, 2017 4:42 pm

Like it or not, I've had to cut coils off of nearly every mag for every caliber MSR I have except 5.56. I just finished a 375SOCOM and it would not cycle without reducing the spring pressure of the mag. As long as the mag puts the next round in the travel path of the bolt, the action will cycle. Excess spring tension puts extra bolt travel resistance. If the mag follower travels freely and the mag will push the last round into position, the action will cycle. If you cut too much off, replace the spring. Or stretch it out a little to compensate until it runs. Your results may vary from mine. My rifles run flawlessly.
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Re: 450 BM mags

Postby Texas Sheepdawg » Mon Dec 18, 2017 6:24 pm

I’ve trimmed several of mine in various calibers.
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Re: 450 BM mags

Postby giannid » Mon Dec 18, 2017 8:07 pm

I'm going to try trimming like Hoot suggests.
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Re: 450 BM mags

Postby Bmt85 » Tue Dec 19, 2017 2:13 pm

I've never had to clip coils on any of my mags to get them to run. I take that back I might have clipped a coil from a 30rd 5.56 mag, but that was an experiment to get it to hold 13rds of 450B. One thing I have done to all of my 450B mags, is tweak the feed lips so the rounds angle up a bit, instead of almost completely horizontal.
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Re: 450 BM mags

Postby Avenger10 » Wed Dec 20, 2017 1:32 pm

Bmt85-

Amen!

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