450Bushmaster.net

New here. I've been shooting a 450 for about a year now and am in the process of doing a few upgrades. This forum has been very helpful. It looks like there has been some discussion of a Sig 556 magazine working without any custom tayloring. Anyone tried the Magpul PMAG? Very similar polymer magazine but I can't find any photos that get detailed of the feed plate or lip to determine if it might also work.

I know a few guys have.

I think that if you want to run factory ammo you need to get rid of that ridge in the front of the mag.

Thanks to directions from siringo and wildcatter I was able to successfully convert 2 20 rd pmags for use with the 450B..


1) you need to grind down the standard follower outline far enough that when you insert the first round it will not 'catch/jam' under the feed lips.. It took several tries, but I was able to get it done.. I used a bench grinder and tried that first round, if it caught at all (ie stayed under the feed lips) it was lather, rinse, repeat..

As MB mentioned the Pmag has a ridge down the front of the mag body.. I used a dremel tool to remove it from end as far as i could reach.. Then i bought a small triangle file ($5 from Tractor Supply/Lowes etc) and did the tediuos task filing the center part of the ridge down

You also need to install some nylon screws in the follower - otherwise it will tilt and jam.. See the post called 'magazines' for pics of Siringos modified followers.. Or I can post pics of my own after I get back from hunting this morning..

aFter the first modification it only took me about 20 minutes to do the second mag.. So far they have functioned 100%

Brian

I appreciate the replys. Sounds like if I want to keep it simple, the known-good is the Sig. I have no functional reason to prefer the PMAG, just aesthetics and brand loyalty but neither of those outweigh the simplicity of a mag that happens to work out of box.

odgreen wrote:I appreciate the replys. Sounds like if I want to keep it simple, the known-good is the Sig. I have no functional reason to prefer the PMAG, just aesthetics and brand loyalty but neither of those outweigh the simplicity of a mag that happens to work out of box.

I personally dont like how long the 30 rd mags are so that is why i went with the 20's.. The BM OEM mag is stainless steel - which i 'think' I read someplace was done because the aluminum mags may expand at the seams when left loaded

The pmag conversion is pretty easy, so dont let it scare you off from trying..

Brian

Something to keep in mind when using these mags. The BM SS mag positions the cartridge higher than any of the others. This mag will feed just about anything, including an empty case! The modified Magpul (refer to past posts) works well with FXT's, 300's, 240's, and most flat point bullets. However, the cartridges do not ride as high as the BM mag and some flatpoints may jam on the feed ramp. The sig mag positions the cartridge the lowest of all three. It is flawless with the FXT's, but can be problematic with other bullet points. Just my thoughts! I personally like the pmag because I can load 7 (it will hold 8) and clip on the top feed lip protector and leave it loaded -- not having to worry about the magazine lips spreading.