Dagger slide consistently locking back with 1 round left in magazine when using Magpul PMAGs

PSA Products Dagger
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Hi guys. I recently purchased a Dagger compact to replace a .45ACP 1911 and a .357mag snub nosed revolver as my EDC. I figure it was time to take advantage of higher capacity firearms, less recoil, and utilize modern ammo advancements to have a more “efficient” self defense pistol in a wider array of scenarios.

So far, I have put about 650 rounds or so through the pistol, and it has functioned great. The reliability, shootability, and overall function of this firearm is wonderful.

At about 500 rounds in, I installed a Ghost Inc Extended Forward Bullet slide release on the Dagger. The reasoning for this is that as a left handed shooter, manipulating the standard slide release button to lock the slide to the rear or to let the slide slam forward was difficult or maybe impossible to do without at least slightly breaking my shooting grip. I prefer to be able to maintain shooting grip while utilizing the controls on my firearm, and the Ghost Inc Extended Forward Bullet Slide Release location on the Dagger put it in a position that I am able to utilize the slide controls without breaking shooting grip.

However ever since I installed the extended forward slide release button, when using PMAGs for the Dagger, the slide locks back with one round left in the magazine. When this happens, pulling back on the slide release does not release the slide and chamber the last round in the magazine. No matter how much I pull on the locked slide, the slide does not move from the locked back position. However, if I press down on the bullet slide release, then the slide does slam forward and it chambers the last round in the PMAG. I can also drop the magazine and then pull back on the slide to allow it to slam/slide forward into battery. It makes me think there is some sort of interaction between the PMAGs and the slide release button, possibly also something to do with the ammo.

The ammo used is ZSR 115grain Full Metal Jacket. I currently only have ZSR 115 Full Metal Jacket and my self defense rounds. I don’t want to waste my self defense rounds testing this, because they work fine in the Glock mags and their price makes me want to avoid shooting them with my current finances. When I get some more plinking ammo, I will test to see if other 9mm ammo causes the same malfunction described when using the PMAGs.

This happens to both of the PMAGs I own. When using Glock OEM mags, I do not encounter this problem. Has anyone else encountered this issue or an issue similar to this?

I know it is not me pressing up on the slide release button when shooting, as I am a left handed shooter and my thumbs are on the opposite side of the slide release. It only happens when there is 1 round left in the PMAGs. Thanks for any advice or insight you guys can provide!

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thats odd, ive never heard of that happening, especially since it is happening to all your pmags, and none of your glock mags. perhaps someone with more mag experience can chime in here and let us know something as to a possible cause for this phenomenon occuring.

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First thing to look at is the plastic follower in the mag where it interacts with the slide release lever and see how and/or where it’s activating the slide release lever.

Somewhere its engaging it prematurely.

The solution is run Glock mags for now. Or for whenever it matters. Pmags for fun, Glock mags for defense.

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I may have 2 PMAGS I may or may not have got with a Sabre Dagger. Neither are of any real use. Both swell on full load. 2 shots to not disappoint and PMAG failed.

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odd, ihavent had that issue with any of my pmags but im not ruling out it happens. oooooh a sabre dagger!?!?! nice!!

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Thank you for the reply and advice in how to begin to diagnose the issue. I have manually hand cycled the rounds through the PMAG slowly. When cycled slowly by hand, there is no issue and the final round in the magazine is fed and chambered.

However, when I cycle by hand with more force with quick snappy motions, attempting to simulate a firearm’s recoil, the last round in the PMAG fails to feed and the slide is locked back to the rear in the manner as described in the first post.

It seems the plastic follower is not actually pressing up on the internal slide release lever when the slide locks back to the rear with one round left in the magazine. There is a clear space between the slide release lever on the inside of the slide that gets pressed upwards to lock the slide to the rear by the plastic follower and the plastic follower. That sentence is a mouthful, and I am sorry if it is a bit hard to digest.

It does not rule out that under standard recoil, a part of the plastic follower jostles and oscillates enough to contact the slide release lever and presses the slide release lever up to lock the slide to the rear when there is one round left in the magazine. There is a large open area and the plastic follower is clearly exposed when loaded with the ZSR 115 grain FMJ rounds. And maybe once the recoil impulse is over from the shot, then the plastic follower’s oscillation ceases and when looking at the malfunction, it appears that the plastic follower is no longer pressing up on slide release lever. It is still weird though that even though the plastic follower is not actively pressing up on the slide release lever as in the case of an empty magazine, I am still unable to pull the slide back to release the slide lock to allow the slide to slam/ride forward.

With this development, it is possible that I may be limp wristing the pistol, but I doubt that is likely. I am shooting with a firm isometric pressure on the grips, and have never encountered this malfunction until I changed out the slide release to the Ghost Inc release. As stated before it does not occur with Glock mags, so I doubt limp wristing is the cause of this malfunction either.

Yeah, definitely not carrying the PMAGs around now for self defense. On the positive side, those PMAGs are now good for training going through immediate action and then to remedial action drills for a pistol. Immediate action fails and then move to remedial action. My sneaker mags if I ever want to train someone to shoot and correct malfunctions.

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Beyond this new development with PMAGs, I originally ordered 2 PMAGs with the Dagger I put together. There were other issues with it compared to the Glock mag that I did not like, so they were already relegated as range only mags. I had trust in Magpul products from my time in service and my exposure to their weapon and magazine accessories. But with how they function with the Dagger, I was disappointed with the PMAGs as well.

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Love PMAGs in an AR. Glock 9 platform my experience has not been good. They repeat issues in a Glock as well.

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As far as the slide release being problematic. Your trigger finger should be out of the trigger well on a mag change. Try sliding your trigger finger on top of the slide release hold minimal downward pressure and insert the mag with authority. No need to draw the slide. I’m a lefty as well and no need to change any parts.

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I have seen a case of this kind of thing happening in one other gun. Ruger Security 9. The springs in those mags are pretty weak, and under recoil the follower wouldn’t be able to overcome recoil momentum, allowing the top round to nose up and hit the slide lock, pressing it upwards.
Never had it happen on a Glock with any mag brand I’ve tried. Same deal with the Dagger itself, two of them.

Even my worn Pmags don’t do that so not sure where the issue is here.

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Finger is always out the trigger well when changing mags or not actively engaging a target. I am not sure if I somehow construed the fact my finger is still in the trigger well, but if I did, I apologize for that.

I do have a tendency to already slam the mags in when loading or reloading, just out of habit to make sure magazines seat and are inserted properly. Maybe the size of your fingers and hands are different than mine, but my trigger finger does not and cannot reach the slide release without having to shift my shooting grip to utilize the slide release with the standard slide release. It is a small shift and change, but it is still a change and shift I do not like and want to avoid.

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I am guessing maybe I incorrectly installed the aftermarket slide release. However the magazine and firearm passes a function check. I am really not sure, nor am I too certain in how to problem shoot it.

I guess at some point I can install the orignal slide release and see if the problem goes away. If it does, maybe it is just some combination of PMAG, ammo used, and slide release interaction.

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Pmags are known to have issues. Google is your friend.

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I have a ton of them and never had an issue. Even my old worn out ones from almost 10 years ago still function. They have a combined 12k rounds through the old batch.

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Interesting. Maybe batch quality is an issue now. When I first got my PMAGs, I already had small issues I did not like about them. They were a pain to fully load at first, but they broke in. However the plastic feed lip already started wearing on them. They have a bad habit of not sliding out the magazine well when the magazine release button is pressed, especially when there are a few rounds left in the magazine. Even with empty mags, the magazines don’t always fall out when pressing the magazine release. I also do not like their magazine base plate compared to Glock’s magazines. The way they lock in the Dagger is a bit more ambiguous than the Glock mags, though slamming the mags in the magwell with firm and fast pressure takes away the ambiguity by brute forcing the action.

Many small issues, and now with the major issue since I installed the new extended forward slide release. Definitely relegated to just range shooting for me.

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As a left-handed shooter for 35 years, lose the after-market slide release & train to run your slide overhand. Even with all the ambi-slide release models these days, I still overhand every one of them.

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Good advice. I got a Glock mag in FDE to match my FDE Dagger. That being said, I’ve not had problems with P Mags (Dagger or AR10/15).

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Pmag should’ve done that metal reinforcement like glock

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Kept my pmags loaded for years in hot/cold cars and they never split or spread. Magpul polymer is good. MFT, ETS, Thermold and all the others seem to be way behind. Recently had an ETS mag crack from loading/unloading. The ones I keep loaded and leave alone were fine. Just the one in my gun that gets messed with when I unload the gun and put the round back in the mag. Granted it’s also clear plastic, tends to be more brittle.

Only downside to the straight polymer in the glock pmags are if you run uncoated steel cased ammo. It has noticeably more friction, could possibly slow the follower down or get stuck.

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Have exactly 2 PMAG Glocks and both swelled on load. I didn’t need to see any more.