View Full Version : Slide Not Locking Back: Magazine?

September 8, 2011, 09:54 PM
Hey all,
This should be short and to the point. Recently picked up a Sig P229 in 9mm. Shoots beautifully, love it. Tonight was the first range visit and I shot 150 rounds of ammo. I noticed that on 1 of the 2 magazines the gun came with, and it only happened with that magazine, that the slide didn't lock back when the magazine was empty. If I racked the slide back on that magazine by hand when it was empty it seemed to hold the slide fine, but not while firing. It wasn't every time that it wouldn't hold however, say 2/3 times? I couldn't see any obvious issues with the magazine lips, but I didn't take out a magnifying glass either.

Can this be the fault of the magazine? If so, would SIG be willing to send me another (based off of the personal experience you might have had)?


Misssissippi Dave
September 8, 2011, 10:29 PM
You might take apart the magazine and clean it inside. You can use a dry lube inside the magazine or just leave it dry (No oil). Also check to see if the spring is straight or not.

If you do call Sig, I suggest calling before 10 A.M. eastern time or after 2 P.M. eastern time Tuesday through Thursday. Then you will get through to someone pretty fast. The wait time on Monday and Friday or during lunch time can be a pain.

September 8, 2011, 10:37 PM
If it consistently happens with one magazine, but consistently does not happen with the other, I think it is safe to rule out operator error and say it is the magazine.

Problem could be fixed with a takedown and cleaning, or possibly a magazine spring replacement. Worst case, get new magazines. Spares are useful for practice, classes, and competition anyway.

September 8, 2011, 10:40 PM
I did clean the magazines out with CLP and then dried them with a cloth. I will check to see if the spring is straight.

Misssissippi Dave
September 8, 2011, 10:45 PM
One other thing to look at. Remove the slide. Insert the empty magazine. The release lever should raise up. There is a small lever on the left side that pushed up by the follower of the magazine. Seeing what does or doesn't happen might be all you need to do. It should tell you if the problem is with the magazine or not most likely.

September 8, 2011, 11:54 PM
I will check to see if the spring is straight

Also check to see that the spring is in correctly. Match it with the spring in the mag thats working correctly.

September 9, 2011, 12:16 AM
If the slide is failing to lock back on the last round fired it could be the ammo causing the problem. I had a similar issue with a new pistol. I changed ammo and the problem went away.

September 9, 2011, 07:52 AM
The release lever is raising properly.

The baseplate is actually attached to the spring and is contoured to the shape of the magazine. Regardless the spring seems ok.

Good point. I can't remember if when the issues went away when I switched ammo. I used 3 different brands, Remington UMC, Federal Champion, and Magtech. I know I had the issue with the Remington UMC, can't remember about the other two.

Misssissippi Dave
September 9, 2011, 07:31 PM
I have had some UMC ammo that seemed to be a light load. This could cause the problem when shooting a new pistol. I never had a problem with the Federal Champion that I can remember. I have shot several cases of the Federal. It has been too long since I used Magtech to remember much about them. You might want to put a piece of tape on the bottom of the magazines with numbers on them. It might make it easier to find out if it is really one or the other. Once you have determined which is the problem try different ammo and maybe even shooting left handed to remove the possiblity of a thumb coming in contact with the slide release.

September 9, 2011, 11:13 PM
Way ahead of you :). I've had mag issues before with a 1911 and used the same advice, works great. The gun only came with two mags, but I put a piece of tape on the one having the issues. It was only that one, but I started with Remington UMC, went to the Federal Champ, and ended with Magtech and I can't remember the timeline too well, was distracted by how great it shot :o. I normally only shoot Fed Champ these days, the UMC was bought for me by my wife, gotta love her :D, and the Mag was what the range sells.

Going tomorrow for another round of testing. I'd be surprised if it was the magazine as for the life of me I can't see anything wrong with it, at least not anything different between it and the magazine that worked. I will report back.

Walt Sherrill
September 10, 2011, 10:04 AM
A weak mag spring is the most likely culprit, if it's just one mag. You can get a replacement spring from Wolff springs (www.gunsprings.com), but it makes more sense to get several, as the shipping cost is about the same. Stow the extras away -- as the other mag spring may eventually weaken, too.

(Offhand, I can't think of a "failure to lock back" problem that could be attributed to ammo. That's because the last (possibly faulty) round is already out of the picture -- extracted and ejected -- when the slide is trying to lock up. Am I overlooking something?)

September 10, 2011, 12:28 PM
@ Walt
All I know if that I ran another 100 rounds through that one magazine today of Federal Champion without a single issue. I guess the only way to prove it was the ammo would be to get another box of Remington UMC and see if it happens again.

My understanding is that if the powder charge is too light the round might still extract but the slide might not get pushed far enough back to the point where it would lock. I could be wrong but that's what I've heard.

Walt Sherrill
September 10, 2011, 02:17 PM
Tunnel Rat:

THAT (weak ammo or, more likely, too strong a recoil spring) could explain things if the failure to lock back occured with both mags, but NOT if it was only one. And we are talking about problems with only ONE (of two) magazines, right?

If it were really the ammo causing the problem, it should cause the same problem with either mags, not just one. (After all, the cartridges don't know which mag they're in...)

You don't have to shoot a MAG FULL of ammo to test your mags or theory: just load two or three rounds in a mag and fire away. Try it with both mags.

I'll bet one of the mags is noticeably easier to load, if it's weak springs. Check that, too.

Misssissippi Dave
September 10, 2011, 07:49 PM
One combination of things may have caused the problem. P229 slide springs when new tend to be rather stiff. I normally lock the slide to the rear for a day or two when I replace mine to allow it to take a set. It helps with feed, ejection and locking after the last round problems. Just shooting the pistol will do the same thing but you get to do jam drills possibly. It takes just a little more distance to move the slide to lock to the rear then it takes to strip another round from the magazine. It isn't much but it is there. You may have solved the problem when you check the magazine and put it back togeter again the right way. The slide lock return spring could also have been a bit stiff until it got moved a few times in use.

You didn't have any problems the last time out so you might not have any problems in the future. I suggest runing a hundred rounds through each magazine and if all is well you can chalk it up to some kind of break in for the magazine and slide lock return spring. Loading only a few rounds per magazine sounds like the best solution to seeing if the problem is gone.

September 11, 2011, 09:01 AM
Tunnel Rat...interesting Site name...if you were a Nam era "Tunnel Rat", God bless you for your service...

A call to the manuf. is in order...to let them sort out the problem...before changing springs etc. At worst, you'll get to know the customer service policies...and that's never bad.

That said, Your problem sounds like a magazine issue...if one works and the other doesn't .... and that's a manuf. problem.

Too, underpowered rounds, (some factory ammunition has been down-loaded over the years, so it's not inconceivable) can cause a failure to eject.

Mleake's suggestion regarding a good thorough cleaning is right on the mark as well.


September 12, 2011, 12:06 AM
One quick test you can do for free: Mark the mags and swap the springs. If the problem goes to the other mag, you need 'to replace both' with new springs. If one is giving troubles, the other may follow soon.

The follower can be swapped next if no change occurs with the spring swap.

Then call Sig.

Everyone DID notice how old this thread is, didn't you?:eek::D

September 12, 2011, 08:45 AM
1SOW, I think you are looking at the OP's join date (May 22, 2011), not the thread date (September 8, 2011).

September 17, 2011, 10:43 AM
I have the same problem with a few of my SIG P226 mag's.....
When I stretch the mag's spring they works fine for a number of rounds.. :)

I e-mailed Mec-Gar ( the makers of the mags) but I have never received a reply :confused:

This thread reminds me to do more follow up..
I feel it's a magizine issue and not the gun. (At least in my case).

Good Luck,


Walt Sherrill
September 17, 2011, 02:36 PM
When I stretch the mag's spring they works fine for a number of rounds...

Yup, sounds like a mag spring problem. Note: stretching the springs degrades the springs further -- so do that only as a last resort. A few more stretches and they probably won't do crap.

You can get new springs from Wolff Springs. Mec-Gar is a hard company to get a response from -- but they make good mags.