View Full Version : Mags refuse to fully seat in AR-15 mag well

Joe Brower
May 13, 2002, 03:13 PM
Howdy, folks;

I have a friend who bought an Olympic Arms AR-15 at a gunshow some years ago, and it's never been right. The problem: When you insert a magazine into the well, you have to SLAM the sucker to get it to fully seat in the well. Conversely, magazines don't drop free, either. You have to forceably tug on them to remove them.

This problem exists no matter what kind of magazine you try. I've tried many.

This problem exists no matter what upper is installed on the lower. I've put three different uppers on this Olympic Arms lower receiver, and the problem persists. Interestingly, the problem doesn't exist if no upper is installed. Of course, this makes shooting the thing a problem!

I've swapped magazine releases and bolt catches with brand new Bushmaster components. No change.

I'm guessing that dimensionally there is something goofy with the lower, although why that would change when an upper is mounted on it I have no idea. A visual inspection by my (admittedly unskilled) eye reveals no differences between this problem lower and the one on my Colt R6601, which works flawlessly. I also note no defects of any kind that could cause a magazine to bind in the well.

Anyone got any clues to offer? I (and my friend) would sure appreciate it!

May 13, 2002, 05:15 PM
My guess would be that maybe the mag release is not in the correct location on the lower, but it's awful hard to say without seeing the gun and having the tools to measure...

J.R. Bob Dobbs
May 13, 2002, 06:02 PM
I've got an Oly that runs 100%. But not all USGI mags will fit nicely, some do and some don't, indicating that there is a variation in the mags, combined with a tight magwell. I've had the best luck with DSL Sanchez mags. When I bought the gun, I got lots of mags, kept the ones that fit, sold the rest.

Maybe your buddy just needs to try some more, or send it back to Oly to enlarge the magwell.

Badger Arms
May 13, 2002, 09:54 PM
When loading FULL magazines into the mag well with a closed bolt, the top round impinges against the bolt carrier requiring more force to seat it. This is normal. You shouldn't be inserting full magazines into the gun without the bolt locked back in tactical situations anyhow. Tell me, does it do this with an empty magazine as well? If so, you might have a problem. Dropping free is a function of how tight the well is but you say this problem clears up without the upper on the gun. This too points toward the same problem.

It is likely that the magazine release is placed too high in the mag well. To test my theory, get another gun you know is not out of spec and measure the distance from the mag release window on the left side to the top of the lower receiver. The top of the mag release opening is .690" from the top of the receiver on my calipers with my Bushy lower. Some judicious filing on the top of the mag release can solve this problem or, if it's a newer Oly Arms gun, you can and should send it back to them for a replacement. Anybody get different measurements?

Steve Smith
May 14, 2002, 03:37 PM
I have read a couple of posters on ar15.com say that the interior dimensions of the Oly mag well are on the small side. That sucks.

Try Orlites?

Joe Brower
May 15, 2002, 03:55 PM
Thanks for all the good input guys. I should have mentioned that I myself have two pre-ban Olys and they're both fine. I also tried many mags in the rifle: Colt, Adventure Line, Sanchez, Center, OK & Parsons, -- hell, I even tried my Bushmaster 5-round hunting mag, and all, empty or full, exhibit the same problem.

It's my opinion at this point that the problem is, as Badger Arms said, that the mag release is too high in the well. My friend is bringing his rifle over this weekend for another crack at resolving this issue, and we shall see what the deal is then.

I appreciate the input. Thanks again!

May 15, 2002, 08:50 PM
I once bought a factory built AR that had problems with certain mags. Just for fun once I rotated the trigger guard down and the problem mags would then fit fine. 5 minutes later and a little file work all was well. Hopefully it is something simple like this and not a tight mag well or mis-located mag release. Good Luck.

4V50 Gary
May 19, 2002, 06:56 AM
Heard the same thing about Oly mag wells being undersized. Anybody got drawings for the lower? If anyone does, please post the dimensions for the mag well so Joe can measure his and see whether its within specification or not.

Joe Brower
May 19, 2002, 09:24 AM
Thanks again for the input guys. My friend brought his Oly by yesterday and we spent an hour or two going over things. To make a long story short, the problem is indeed the fact that the cut in the lower for the magazine catch is too low, by approximately .025". The well itself does not appear to be undersized or out of dimension, at least, not enough to factor here.

Badger Arms posted that on a Bushmaster he owns, the distance he measured, using calipers, from the mag release window on the left side to the top of the lower receiver, was .690". I performed the same test on my Colt R6601 and got .688. Well, when I measure our problem child, it reads at .665". This is just enough to require the amount of force I've previously reported in order to fully seat the mag, and then when the mag release is pressed, the parts are under enough unneeded stress to require the mags to be pulled from the well -- they will not drop free. But a firm tug and they do pull free with no apparent damage. The fact that the mags are aluminum makes this doable.

Given my lack of proper skills to feel comfortable in filing away at the problem lower (especially not one that's mine!), we have decided to just keep things as-is, at least for now, since the rifle is functional in it's current state, if not optimal. My friend will be calling Oly this week and see what they have to say about the matter, since it's their goof. From the serial number on the pre-ban lower, it appears that this was one that was cranked out just before the Sept. 13, 1994 AW-ban deadline came down, and my theory is that they were running their manufacturing equipment just a bit too long between maintence/tuning cycles, which caused tolerances too wander a bit too far out of spec, and probs like this were the result.

In any case, that's where things rest for now. Thanks again to all who took the time to respond! I'll keep you updated on what Oly has to say and anything else that's worthy of note.

May 19, 2002, 09:56 AM
Since it's a pre-ban, if you have actually assembled a pre-ban rifle, you'll probably want to repair it, since the warranty has long since run out, and Oly may well "replace" it with a post-ban, if at all. :)

Badger Arms
May 19, 2002, 12:15 PM
It's a simple fix. Simply file on the magazine catch, not the lower. This is a very cheap part. If you grip it in a vice, just file that .025" from the TOP of the catch to where that area that protrudes into the mag well is indeed at the right height. This will not prevent the overinsertion, but the magazine will not have to be overinserted to seat it at least. Hard to explain so I've uploaded a picture to illustrate. It's not to scale.

4V50 Gary
May 19, 2002, 05:42 PM
Concur with BadgerArms. As a general rule, when working on guns, modify or attempt to correct the problem by working on the "cheap" parts first since mistakes are easier (and less costly) to rectify.

Joe Brower
May 20, 2002, 07:05 AM
Badger Arms;

Outstanding idea. I will give that a try and let y'all know the results. At worst, I'll goof up a $5 part. I sure appreciate your good advice and you taking the time to share it!

Joe Brower
June 18, 2002, 08:50 AM
OK, folks, I finally got this rifle from my friend, worked on it over the weekend, and here are my results as promised. I removed the mag catch and filed down the "shelf" portion of it down a ways in order to lower it's bearing surface where it catches the mag and clicks into place. I ended up removing a lot more than just .025" of material, and the rifle is considerably improved, but it's still not 100% right. It's functional, though, and performance varies depending on what mags are used and how full they are. Needless to say, a full 30-rounder still takes a bit of pressure to seat, and still needs to be tugged free when empty, but it's a fair bit better than it was.

So, thanks to everyone for your time and ideas. I sure appreciate it, and so does my friend. Next stop is the range to put a BSZ on the puppy.