Mystery Glock Jams

[chp5]

Mystery Glock Jams at Alabama state match

At the Alabama state match last weekend, I shot my Glock 35. It has a brass THE magwell and I use Glock factory hi caps and Arredondo +5 extensions with +10% mag springs. I shoot 180 grain Rainiers loaded to 1.125 OAL.

I had two nasty jams of two separate stages. In both, I had a mag change, shot one or two shots (I can’t remember the exact #) and then the slide locked back. The slide would NOT release and the mag would NOT drop out. In both cases, I attempted a tap-rack-roll and it did not clear the jam and the slide stayed in the locked position. When I looked into the open ejection port (the slide was locked back) there was no spent brass and it looked as though I had simply locked the slide back on a full mag – although I didn’t study it – I just tried to get the gun running again.

Each one of these jams cost me approx 5 seconds (I’m guessing).

Here’s the kicker: After the match I shot each mag and they all ran 100%!!??

I’ve had NO problems with these mags or the gun before the match. Here’s what I think could be the cause(s):

1. OAL TOO LONG: I’ve always loaded my Glock rounds in extended mags to 1.125 OAL. I checked my rounds when I got home and they were right on 1.125.

2. BAD MAG SPRINGS OR FOLLOWERS: Again, I’ve never had any problems with the mags. I’ve put approx 15,000 through the mags with 100% reliability.

3. OVER INSERTION OF THE MAGS: Maybe my adrenaline got the best of me at the match and I jammed the mags home on the mag change and over inserted the mags. However, the mag base plate fits very snug on the THE brass magwell. I’ve studied it and it seems doubtful that I could over insert the mags.

It’s frustrating because I can’t reproduce the jam. But guaranteed – I’ll reproduce it in the next match!

I WOULD APPRECIATE ANY THOUGHTS/HELP YOU GUYS CAN GIVE.

Also – what do you guys thing about modifying the slide catch so it doesn’t lock the slide back? Useful modification? If so, why? How do you do the modification?

Thanks.

Cy

[cpty1]

I'm thinking you accidentally hit the slide release. You probably changed your grip just enough after the reload to something different than your grip on the draw. Some Glock shooters have trouble with the extended slide release. You (at least I) can do things in a match that can't be duplicated in practice. I played around with some oversize mag release buttons at one point. Tons of dry fire and live fire practice with no problems. Go to a match and you guessed it...mags falling everywhere. You might try two things. If you have an extended slide release, replace it with a standard length one; or modify the long one so it doesn't engage. Shooting Lim-10 or production I wouldn't do that, but limited would be no big deal and I'd do it in a heartbeat if I thought that was my problem. BTW I didn't have that spring with me this weekend but I'll get it to you Wednesday night if you go to Bullseye. Congrats on your win at Alabama.

[Little Bill]

Cy-

I think that Chris is on the right track to your problem. How many rounds were in your mag (apprx) when the malfunctions occured? What did you finally do to clear the malfunction? Was it the same mag both times? What type of glock follower are you using (9mm1, 2183, etc) or is it Arredondo? It could have possibly had a follower malfunction and become tilted, causing rounds to tilt and then a round to hang up the slide release, also causing the mag to bind and not drop free. Kinda doubtful though. I would be leaning towards accidental slide release contact. I have done that on a few occasions with the factory extended release on my G34. Hope this helps-

Bill

(edited because of my lack of eduucaztion)

[chp5]

Thanks Chris.

I only use the standard (non-extended) slide release because of the reasons you stated.

I considered whether I accidentaly hit the slide stop, but that would not explain why the slide would not release from the locked-back position and why the mag would not come out of the gun.

BTW - does anyone use the Arredonndo followers for Glocks?

[chp5]

Thanks Bill.

I'm using the stock Glock hi cap .40 follower. I think the stock # is 1048 or something like that.

The mags were almost completely full when the jam occured. I'm not sure if the same mag was involved in both jams.

To finally clear the malfunctions (the slide was locked back and would not move), I had to press the mag button and rip the mag out with my left hand. I believe that the slide fell forward when I ripped the mag out (I'm not 100% sure of this - I was frantically trying to get the gun running again). I then inserted a new mag and pulled the trigger on an empty chamber. I then racked the slide and finished the stage.

Bill and Chris - do you guys modify the slide release so that it does not lock the slide back on an empty mag?

Thanks for your thoughts.

[cpty1]

Didn't catch the piece about the slide not releasing at all. I leave the slide release as is on all my guns, but I don't have a problem with hitting it accidentally either. I use the Arredondo extensions with the stock followers as well, with no problems. Check a couple of things: the mag catch to be sure it isn't worn, and also the mag "slot" to be sure it hasn't gotten burred or something. Does sound like the problem was mag related.

[Little Bill]

Cy-

I went to a standard size release. At the same time I added an "A-grip" (like moleskin) to the gun, and I think that helped prevent any further hand / finger contact. The mag over-insertsion could cause the malfunction, but I dont' know why it wouldn't happen on the first shot w/ the over-inserted mag. Very interesting problem.

[Flexmoney]

1. OAL TOO LONG: I’ve always loaded my Glock rounds in extended mags to 1.125 OAL. I checked my rounds when I got home and they were right on 1.125.

1.125 is not too long...not by a long shot. In fact, I don't load 40 any shorter than 1.135 OAL. (less chance of pressure spikes)

Things I'd check:

- mag lip width. http://www.custom-glock.com/magtech2.html

- clearence between your pads and magwell...with a look at how that might impact the mag catch

- tightness of the magwell screw (can torque the frame)

[chp5]

Thanks Flex.

I just re-installed my mag well, so I'll go check the tightness of the screw. Any guidelines for tightnesss? Thanks.

[Flexmoney]

Any guidelines for tightnesss?

I can't help there...I don't use one. I have seen a number of post where that (overly tight) has been a problem though.

[eric nielsen]

Any time I practiced any sort of leaning barricade-type position with my G35 it would lock back early. Palm of my left hand did it during recoil.

Attempting to squeeze the extended part (with plyers) so it would hug the frame closer, I - oops - snapped the lever right off the part. Put it back in the gun & that's what I've used ever since.

I did buy the non-extended one, thinking maybe I'd want it for Production or L10 or IDPA or something... haven't used it yet.

dvc - eric - a28026

[chp5]

Thanks forth replies.

It's definately not me hitting the slide lock with my left hand.

Could the jams be caused by limp wristing? Could limp writing cause the slide to lock back prematurely?

[Yar]

I had a similar problem when i replaced the slide lock/release improperly after a detail stripping. Look to make sure the wire nubbin is under the top locking block pin.

[chp5]

Thanks Yar. I'll take a look.

[Flexmoney]

It's definately not me hitting the slide lock with my left hand.

Could the jams be caused by limp wristing? Could limp writing cause the slide to lock back prematurely?

The right thumb is what would hit for me.

have you checked those mag lips?

[chp5]

Flex -

I'm not hitting the slide lock/release and locking the slide back because releasing the slide release and/or racking the slide (both of which I tired) would have solved the problem.

Yep - mic'ed the mag lips and they're within specs.

I THINK I'VE IDENTIFIED THE PROBLEM:

What I think is happening is that the slide moves to the rear, then starts to come forward and strip the top round in the mag for insertion into the chamber. At that point, the nose of the round gets stuck on the ramp in a horizontal position - thus stoping the slide (in the "almost locked back position") and also keeping the mag from dropping when I push the mag release button (and requiring me to rip the mag out of the gun).

What could cause this type of malfunction?

* weak mag springs?

* bad follower?

* too heavy recoil spring (I use the stock recoil spring with an approx 170 PF load)?

* limp wristing?

* OAL too short?

Thanks for your thoughts guys.

Cy

[Nik Habicht]

Cy,

When you pull the gun apart, is there jacket material build-up on the edge of the ramp? I had two of these stoppages in recent months ---- after switching to a 133 power factor 147 gr. load in the nine that shoots real soft. Todd Jarrett diagnosed it as loaded too long when he saw the buil-up during a class. After shortening the O.A.L. down, the problem has not re-surfaced in the last 1500 rounds or so.

[mike4045]

I had similar problems and several others. I tried several things and ended removing the steel guide rod from my gun and now it works fine. I have put it thru 2,000 rounds since then. My gun decided to act up at the Space City challenge last month. It was not the first time it had acted up, but it jammed 8 times and cost me at least 1 min. in clearing the jams. I also had failure to completely feed and the mag would not come out. Three bad stages that cost me a shot at winning my class.

Mike4045

[chp5]

Nik and Mike,

OAL:

My OAL on my .40 is 1.125, so I don't think I can load them any shorter. I did, however, get out the Dremil and re-polish the feed ramp to make sure there wasn't any build up.

Guiderod:

I've heard that some Glocks get finiky with after-market guide rods. However, I've previously put approx 15,000 rounds through my G35 with a tungston rod with 0 malfunctions.

I think that my mag springs were weak. I also received some advice that I should only load 19 rounds in my mags with Arredondo +5 extentions in order to avoid spring binding. I've ordered a package of new Wolf +10% mag springs. I'll let everyone know if that fixes the problem.

Thanks.

[Nik Habicht]

Cy,

Another bit of advice from some longtime Limited and Open Shooters. Load all your mags with 15 rounds during the match. When you're in the hole, or on deck, top them off with the last 5 rounds. After the stage unload 'em and fill 'em back up with 15 rounds after cleaning...

[chp5]

Good advice. Thanks Nik.

[Ironman]

I have been following this post and low and behold when I took my 35 out this weekend my slide locked back several times. I had just gotten a trigger job done so I called and talked to the person that did the trigger job. He also said that sometime a small burr will develop on the slide release which has to be filed off. This thread has brought up several other possibilities that I will explore this weekend at the range. What is strange is that I have put about 10,000 rounds through this gun without a failure, got a trigger job done and now it does not want to cycle. There is a 3 gun on Sunday so I have to get it fixed on Saturday or else use my 45 with only 10 round capacity. Those high cap mags can really spoil a guy. I will let you know what I find after this weekend.

Jim

[mcoliver]

Back when I was still messing around with different ammo I had the same lock-back-stuck-round problem. It took me several mag spring switching, guide rod replacement, recoil spring replacement to realize it occured only in a specific ammo: El Dorado starfires. I should've miked the rounds just to compare OAL with the other brands but I just stoped using the problem ammo.

I know my story won't help your problem but here's a thought: "Could there be the slightest possibility your mag isn't inserted high enough to properly position the feeding round in the ramp?" You did say the pads fit snugly w/c I take to mean there's no more upward clearance? Maybe instead of ramming your mag back in to replicate the problem you just slowly insert it enough that the catch "barely" engages.