PMAG® 30 AR 300 B GEN M3™ Review

From Magpul

From Mike Westra

Way back in January Magpul Industries announced a 300blk version of the popular PMAG.  This was great news for the 300blk crowd. Finally a magazine dedicated solely to my round of choice.  According to Magpul Industries the PMAG® 30 AR 300 B GEN M3™ is supposed to handle all the various bullet weights and deliver the same functional reliability we have come to expect from their magazines.  Well it has been several months since the announcement and I have finally got my hands on a couple of the new 300B mags.   I immediately opened the packages. I just could not wait to get my hands on them, not even to get home first.  The 300B is supposed to have a “visual and tactile feel” to help prevent accidentally shooting a 300blk round in a rifle chambered for 5.56.

At first glance I did not notice any difference.  I had to put them side by side before noticing the 300B mags had a more open block texture on the side compared to the 5.56 PMAG. Once you know what the visual differences are it is easy to identify the 300B vs the 5.56 mags.  However for me the difference in texture and feel alone may not be enough to stop me from accidentally inserting the wrong mag into my rifle. Maybe my hands lack the sensitivity needed for me to go only by stock feel. This is not a deal breaker as I normally add grip tape to positively identify my 300blk mags by touch. Your experience may vary.

First thing I did when I got home from the store was dismantle the magazines so I could compare the internals of the 300B with the internals from a 5.56 PMAG.  At quick glance they looked identical other than the color of the followers. The follower in the new PMAG is black where the 5.56 follower is grey.  The spring is the same length and appears to be the same thickness and strength.

However, looking at the magazines from a top view there is a change to the internal magazine rails that guide the follower up and down.

The guide rails on the 300B mags are made slightly smaller which appear to put less side load and drag on the bullets as they feed upward, allowing for a more natural stack. Assembly and disassembly are exactly the same as the Gen 3 5.56PMAG.

I received an unexpected surprise while loading the mags for the first time. The rounds went in so easily they put me in to a euphoric state.  I felt as one with the universe, calmness settled over me.

True Enlightenment was reached.

Honestly they were actually a joy to load. I won’t be needing my Maglula LULA Loader for these.  I loaded 30 rounds of American Eagle 150gr 300blk in the mag and it fit perfectly.  No rattles or play, I did not have to hit the back of the mag on my hand to keep the rounds lined up properly feeding.

I wanted to get a fair comparison so I brought my 5.56 PMAG with me out to the range and loaded them with the same 300blk ammo from American Eagle. I started with the 300B mags first, they had no problem inserting properly on a closed bolt.  For the first few rounds I fired one round at a time and progressed to a rapid magazine dump.  No failures, the firearm cycled perfectly and locked back after the final round.  I loaded the 5.56 Pmag and proceeded to fire at the same rate, again no failures, cycled perfectly and locked back after the last round.

I personally have never had an issue with any Magpul PMAGs and the new 300blk mags did not disappoint.  Magpul’s 300blk PMAG worked as promised.  The  300B PMAG feeds quickly, and flawlessly. Loading is a breeze.  Other than adding something to assist me with the tactile identification I see myself having no issues with the magazines in the future.  Now I have to ask myself, “Do they function well enough to justify replacing the mags I currently use in my rifle?”

I’m certainly not giving up these new mags but whether you replace your entire stock of mags or not for 300 Blackout is up to you.

Mike Westra
Mike relies on the on the knowledge, skills and attitude he developed while working as a deputy sheriff, bounty hunter, and firefighter to educate and train his students and customers. Mike manages a gun store and is also the Lead Firearms Instructor with Ammo-Inc. On his days off you can find him tearing up the skies over Michigan in a Cessna. #mikeisawesome