I meant specifically the round flying out. I've had no problems with my m3 mags. And they fit the same in the acr. Haven't used one as a mono pod yet though.

Also I'd like to see someone chip the over insertion tab off of one.. you'd have to try.

 

Nope. They spit rounds just like the others. PMAG's are better in this regard than some of the other plastic mags on the market but they'll still do it.

I have four Gen3 mags that I bought specifically to run in my ACR. All four have a chip on the tab below the mag catch slot. This is the area that chips not the small tang on the rear of the tube.

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Oh I thought you meant the one on the back. I'll have to check mine for chips. I got 25 and have been only running them since. Plus two 40 rounders. I have tried many times to get any mag to pop rounds out and I can't do it. I find it odd that the new ones do with your gun. Something is off about it.

 

I emailed Remington and Bushmaster and sent them links to my videos. I never heard anything back. I also contacted Mapgul via an employee who posts on another forum. This fellow told me the ACR was spec'ed and built to run the original PMAG before we had the Rev M, Gen2, Gen3, etc.

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That's probably true about it being made to work with the original p mag.

However, your rifle is just about the only one that pops rounds with little effort. I'd be up bushmasters ass if it was my rifle.

 

I thought I'd seen a few other users reporting that their guns would spit rounds too especially with the Troy mags.

Interestingly, the FN SCAR does the same thing with plastic mags since it doesn't have any internal stops either. IWI got it right with the Tavor.

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Have you checked if the bolt catch hits the rim of the cartridge? This is about the only thing that can explain your problem. Overinsertion can not ne the problem unless the force is excessive.

 

The only way I can make it happen is to get the mag part way into the well, and then slam it home with a stupid amount of force, while the bolt is locked open. No way it would ever happen during normal operation.

 

Over insertion is the wrong description. It isn't that the mags are going in too far it is that there's nothing inside the gun to support the flexible feed lips on the plastic mags. Inertia is causing the top round to push up through the lip on the magazine.

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But some guns do it, some don't. That's what's weird.

 

I think they'll all do it with the right combination of factors. Note too that steel or aluminum mags don't pop rounds since they don't have the "built in" flex of the plastic mags.

If and when the AK compatible lower becomes available I'll probably run my ACR 99% of the time as a 7.62x39 or a 5.45x39 depending on which magazine formats are available. For those times that I do use 5.56 I'll probably run the gun with the AK lower in place and use Galil magazines.

Happy New Year, everyone!

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Gen3 Pmags prevent this.

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I just did the test over again. With my black acr and gen m2 mags, they won't pop out. But when I slam it home it over inserts. With gen m3 mags I can pop them out. But it takes some real trying. I have to start the mag a foot away and slam it so hard and hope I hit the mag well. It's a non issue.

The other acr does it with both mags, but again, I really have to slam it. It took several tries and so much force I though something might break. Again, non issue.

You shouldn't ever slam a mag in a gun as hard as that. It's seriously a large amount of force that is needed.

 

I bet if you try the same mags in your AR you won't spit rounds at all. Note in my video also that PMAG's seem to be a bit stiffer than some other plastic mags so they don't spit as badly.

I agree that this whole deal is really a non-issue for 99% of the current user base. But I think it needs to be addressed if the ACR is to be used as a military or LE firearm. Depends on what a person does in a high stress moment with a bit of adrenaline

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I bet if you try the same mags in your AR you won't spit rounds at all. Note in my video also that PMAG's seem to be a bit stiffer than some other plastic mags so they don't spit as badly. Try using a Lancer, Troy or Tango Down mag.

I agree that this whole deal is really a non-issue for 99% of the current user base. But I think it needs to be addressed if the ACR is to be used as a military or LE firearm. Depends on what a person does in a high stress moment with a bit of adrenaline coursing through the veins.

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True. I don't have a complete ar at the moment to test but I believe you. Fixing the issue would be good. One less thing to go wrong.

 

I have a ruger sr556 and use the same mags between both guns and on the ACR it just barely lets a round pop out into the chamber. and on the sr556 no over insertion and no rounds pop out again using same mags on both I will have to try the difference between gen2 and gen3.

 

I was able to examine a Costa Mesa ArmaLite AR-180 this morning. I was eager to take it apart since this is the father of the ACR and similar modern designs.

Sure enough. The AR-180's mag well has two "wings" that extend up into the upper to stabilize the magazine, act as an over-insertion stop and cradle and support the magazine feed lips.

The AR-180 had some other issues but it appears to me that the magazine well was not one of the rifle's design issues. I'm pleased to see (and feel vindicated by) my discovery.

I didn't have a camera handy but I'll see if I can't revisit the gun and take some photos tomorrow.

 

Here is the 180's mag well. Note the extensions at the top of the lower that support the feed lips.