AR magazine issue - Drop Free

[JR24]

Hey all, perhaps you AR experts can give me a place to start.

I just picked up a Stoner .300 BLK upper for my M&P lower, gun shoots great so far... BUT 4 of my 5 AR stoner magazines do not latch in well.

One of them runs fine, drops free. (This may be the original mag that came with the rifle)

The other 4 need to be inserted forcefully, even with an empty mag and open bolt. And once I get them latched, I gotta rip them out.

All 5 work fine with my .223 M&P upper.

My original M&P is from around 2008 and had similar problems with magpul mags back then, so I suspect the issue may be with the magwell, but I'm not sure where to start.

Is there a brand of mag to try for problem magwells? Is this probably a lower issue and I'd be best picking up a stripped lower and starting over?

Thanks for any help.

 

[Zerodefect]

All my Mags are Magpul pmags. Except for a couple Colt 20's. Try those.

 

[M1key]

Are they tight going in or just when they lock up? Maybe a new mag catch is in order...

I would try Gen 3 Magpul mags too, but first try to fix the original problem.

M

 

[JR24]

Are they tight going in or just when they lock up? Maybe a new mag catch is in order...

M

Just locking up, it seems like the 4 want to be pushed further into the magwell than the working 5th. Once I get them locked in, removing them requires some force.

Again, all drop free and lock up easy with my first upper.

 

[grampajack]

I just got done building an upper for a guy using primarily AR Stoner parts, which was my first time laying hands on any AR Stoner products. To say I wasn't impressed would be an understatement. I would send back the mags and replace them with pretty much anything else. If my recent experience with that brand was any indication, my money is that the mags are defective. Good AR mags are just too danged cheap to put up with that kind of nonsense.

ETA: Wait, so the upper is AR Stoner, as well?

 

[JR24]

I did order some pmags and we'll see how they go. The stoner mags Ive had for nearly 10 years, and were cheap IIRC.

Im hoping the gen 2 pmags won't give me the issues the first ones I got did, but hey, if this leads to a new lower and rebuild, hey thats fun too.

Sneak the parts past the wife slowly and she'll never realize how one AR became 2...

 

[boom boom]

If you can, return them for credit or new mags. Midway used to be pretty good about returns.

If you keep them, one thing that you can do with the mags is put some magic marker (use the alcohol based stuff, not perma markers, carbon black , or some other removable marking lfuid on the upper part of the mag to see where it is hanging. Lightly sand them using emery cloth in those places or if you have some fine files or stones. Make sure to thoroughly clean the mag afterwards--you do not want that grit in your AR. Repeat until they drop free (I don't recommend altering your lower magwell but that is also an option if you find other types of mags sticking).

It also helps if you wipe them down with a light coat of oil on the exterior initially and every so often.

 

[JR24]

What could cause them to stop dropping free with the second upper? Something in the frame being thicker?

Eventhough Ive owned this gun for nearly 10 years, until recently it has been my least fired rifle, so I'm still an AR neophyte.

 

[FL-NC]

1- AR magazine releases can be adjusted, and sometimes need to be as they wear out 2- if you have a fully loaded mag and are trying to insert it with the bolt FORWARD, they can be difficult to get in or out. Don't know if this is part of the problem or not- but this is why we always loaded them to capacity minus one. 3- You are talking about mass produced things that are stamped and bent sheet metal. Some companies do a better job than others on this.

 

[Hummer70]

From what I am hearing it is hard to diagnose what your problem is as the quality of the available parts is suspect and I understand lower receivers have been found with mislocated pin hole locations.

Mags are supposed to drop free PERIOD

FL/NC is right, works better when mag inserted with bolt to the rear.

do you have problem inserting empty mag?

 

[boom boom]

What could cause them to stop dropping free with the second upper? Something in the frame being thicker?

Eventhough Ive owned this gun for nearly 10 years, until recently it has been my least fired rifle, so I'm still an AR neophyte.

Sometimes poorly made mags can be off spec. Very occasionally, mag walls are too thin and the mag can bulge under full mag pressure.

 

[JR24]

I did some poking around with my calipers and some work on where the mags hang up.

Best I can tell the new upper is likely machined slightly off center. Internal dimensions are the same as much as I can tell but the problem mags hang up on the far rear right corner of the mag, contacting the upper frame.

Measured, that part of the "good" mag is .02" thinner (.885 vs .865) and that extra width is causing the hang.

I suspect the PMAGs I have on ordee might not help but another forum suggested Lancer and looking at the design I can see that they might work.

I plan to go to a local store with my calipers and see if any of their offerings might work, or of they have Lancers.

Ideally I'd prefer finding mags that work over returning the upper, but thats on the table yet.

 

[kBob]

Before I got carried away the first thing I would do would be pay attention to the post #9 by FL-NC.

The mag release on the AR15 system is user adjustable. If mags are hanging up when being released or having a hard time locking in place the first place I would look would be the mag release. "Push the button, Max!" Seriously push the mag release button in with say the eraser end of a pencil until the mag release itself clears the things on the left side of the lower and give it a turn or two to turn it out. We used to do this with our M-16A1s all the time. Frequently new issue guns especially had releases turned all the way in "at the factory" and these would hang up on some magazines. Sometimes guys would go over board on turning out the release and the merest brush against the button by gear or the environment would result in a dropped magazine, especially if it was a loaded magazine. BTW we loaded our 20 rounders two short for both easy loading with the bolt closed and to ensure first and second round feeding and yes actually saw with my own eyes failures of fully loaded 20 rounders and fully loaded thirty rounders so we loaded those three short. But what do guys that had to depend on their ARs for their very lives everyday know about such stuff?

And you could be experiencing the sort of "round out errors" or "Stack Errors" suggested by others where the tolerences "Stack" that is the allowable errors ad up and you end up with a system that does not work properly.

Yes I would look for a Stack error and yes I would consider different magazines, but first I would play with the magazine release a bit as it cost nothing.

-kBob

 

[JR24]

Before I got carried away the first thing I would do would be pay attention to the post #9 by FL-NC.

The mag release on the AR15 system is user adjustable. If mags are hanging up when being released or having a hard time locking in place the first place I would look would be the mag release. "Push the button, Max!" Seriously push the mag release button in with say the eraser end of a pencil until the mag release itself clears the things on the left side of the lower and give it a turn or two to turn it out. We used to do this with our M-16A1s all the time. Frequently new issue guns especially had releases turned all the way in "at the factory" and these would hang up on some magazines. Sometimes guys would go over board on turning out the release and the merest brush against the button by gear or the environment would result in a dropped magazine, especially if it was a loaded magazine. BTW we loaded our 20 rounders two short for both easy loading with the bolt closed and to ensure first and second round feeding and yes actually saw with my own eyes failures of fully loaded 20 rounders and fully loaded thirty rounders so we loaded those three short. But what do guys that had to depend on their ARs for their very lives everyday know about such stuff?

And you could be experiencing the sort of "round out errors" or "Stack Errors" suggested by others where the tolerences "Stack" that is the allowable errors ad up and you end up with a system that does not work properly.

Yes I would look for a Stack error and yes I would consider different magazines, but first I would play with the magazine release a bit as it cost nothing.

-kBob

Tried that, no dice. Was really hoping it was that easy.

 

[grampajack]

I would return that upper to midway and take my business elsewhere. You can get MUCH better parts for maybe 10-20% more.

 

[Creature]

I would return that upper to midway and take my business elsewhere. You can get MUCH better parts for maybe 10-20% more.

This. This. This.

 

[JR24]

I would return that upper to midway and take my business elsewhere. You can get MUCH better parts for maybe 10-20% more.

While solid advice, the thing was on sale for like $350. Its giving me reason to finally start learning the internals of my AR on a limited budget and to dip my toe in the .300 pool.

EDIT: if you can point me to where I can build a better upper for $400 I'm all ears

With my 1 good mag it did shoot reliably and 2" at 100 with 150 grain AE, with my variable 1-4 just braced with my elbows on the bench, which is pretty good for me without a sand bag with any gun. So it is accurate, relative to my skill.

 

[JR24]

Thanks for all your suggestions, I know the issue and have a plan moving forward.

 

[grampajack]

While solid advice, the thing was on sale for like $350. Its giving me reason to finally start learning the internals of my AR on a limited budget and to dip my toe in the .300 pool.

EDIT: if you can point me to where I can build a better upper for $400 I'm all ears

With my 1 good mag it did shoot reliably and 2" at 100 with 150 grain AE, with my variable 1-4 just braced with my elbows on the bench, which is pretty good for me without a sand bag with any gun. So it is accurate, relative to my skill.

I'm pretty sure you can buy a much better complete upper for $400. .300 BLK is now ubiquitous, so they don't really cost anymore than 5.56 these days. Although considering what you're going to spend on ammo, the price of the upper is going to be pretty much irrelevant in the grand scheme of things.

 

[M1key]

Just to make a last comment...I had a few BCM marked aluminum mags that were difficult to lock in even empty, without a bit of a rap on the bottom. I cleaned them up with a few strokes at the notch with a file and they work fine.

M

 

[JR24]

Got the replacement upper back, mags feed and drop free perfect now.