New to 450BM, questions

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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New to 450BM, questions

Postby Hogan » Sun Feb 19, 2017 5:02 pm

I joined the forum a few weeks ago and just been lurking. I bought a 16 inch Bushmaster Factory 450 about two weeks ago from Walsh. I finally got to test fire it today with Hornady factory ammo. All rounds fired and ejected, however, only the first round locked back the bolt on an empty magazine. I fired 9 rounds total and had 8 that short stroked. All ejected at 2:30-3:00. The upper is assembled with a mil-spec collapsable stock. I figured it may need some break in, so I re-lubed the BCG and hope to re-test in a few days. Is there any thing else I should be looking for?

Thanks
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Re: New to 450BM, questions

Postby plant_one » Mon Feb 20, 2017 12:33 am

any new upper should be run dripping wet for at least the first couple boxes of ammo. lube the heck out of the BCG and be prepared for some spray off the bolt for the first round or two.

this applies to any AR15, not just the 450bm.


this allows for parts to wear in and any manufacturing chatter marks or burrs on either the upper or the bolt carrier group to smooth out.


if you want to help speed up the process you can manually cycle the upper at home, unloaded, a bunch of times as well. 150 or 200 cycles should be more than sufficent. This is a very common trick many 300 blk folks do to wear in their uppers for subsonic use when they're new to ensure that there's no break in needed and to eliminate one possible hiccup.



once you're broke in, unless you have one of the fancy BCG's with a supercoating (NiBO or melonite for example), an AR15 bolt carrier group is designed to run lubed. dry is not the ticket for long term success with these guns.
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Re: New to 450BM, questions

Postby Hogan » Wed Mar 08, 2017 3:07 pm

I was still having the same issue. So, last week I emailed Walsh. They advised that there have been some known issues with Bushmaster magazines and that may be the problem. Walsh advised to contact BM and they will ship a new mag as they acknowledge there are some problem magazines that were shipped with uppers. I called and received the new magazine yesterday. Upon loading a round into the new mag, it appears that the rounds sit higher on the feed lips than the original mag. I hope to get some range time this weekend to try it out.
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