300 Blackout in PMAG

[bulletsmith]

I looked a little bit and didn't find a thread about this so here we go.

I loaded my first 300 blk and tried to put them into a generation 2 PMAG. The first thing I noticed is that the rounds do not sit as neatly into the magazine as I thought they would. It seems to take a lot of force to load the mag past 15 rounds. When I tried to run with a magazine loaded with only 20 rounds I experienced a lot of feed problems. The bolt grabs a round, then the round seems to get a little sideways and jams, often...

My research finds that this is a known issue and the gen 3 PMAGS have a different configuration of the internal guide ribs. My metal mags don't seem to suffer from this issue so that's an option.

If you are buying mags for a gun chambered in 300 blk. do your homework. If PMAGs are your choice, you might want to go with the generation 3 versions.

 

[jblomenberg16]

Yep, common issue. Gen 3 mags are better, and sometimes adjusting your seating depth (if you reload) can help as well.

 

[rausch51]

My brother's 300BLK has had similar issues. Oddly, I've run some of my Gen 2 PMags through his gun and never had an issue. He's switched to metal mags for the 300 and had no problems.

 

[tacticalmaster45]

I use Lancer L5AWM (translucent smoke) 20rd mags exclusively for my 300blk needs - helps assure I don't accidentally mix 223/300blk in weapons

 

[Woobie]

D&H makes a 300 BLK mag with a modified internal rib. They're like $11.95 on Bravo Company.

 

[Bfish]

I run gen 2 pmags with my 300blk and I don't have any issues. I can't remember what my overall length is, but it's quite a bit shorter than mag length. 203grain subs. I haven't had any feeding issues is 500+ rounds.

 

[Osprey]

I finally got to shoot my 300BLK and I had new ASC 20 round mags. I thought I had something wrong with my upper or lower since I was having loading issues. The mags fit great empty but had issues when trying to load into the rifle. I literally had to slam the mags to finally lock into place. I was able to finally shoot a few rounds before encountering your PMAGS issues. I ran into this with ASCs with my AR 47 and fixed that problem by loading the magazines and let them stay that way 24-48 hours. I might do the same with the 300BLK mags. It might be the spring on these ASCs as they are very tight.

 

[cop car]

I use Troy mags for my blackout. It's a lot easier than modifying pmags

 

[Slow Hand]

My 125's usually run ok in PMags, but my 235gr subs will lean inward. They do ok in 20 round PMags, so I normally load them in those. I did just get a couple of Lancers after hearing they do better and I will agree. I've inky out a few mags worth downrange but they seem to load better and feed and function was 100% with them.