Failure to lock back

[rottenII]

I was wondering what the main cause for failure of the luger action to lock back? I purchased my first luger this week, an all matching 1937 S/42. I plan on it being a safe queen and show and tell piece but I could not resist at least trying it out. I ran a total of nine 8rd mags through the pistol. Rnds 1-7 perfect every mag. Now for round eight. With four mags of WW white box ball ammo it shot all eight and would not lock back. Using five mags of reloads (4.5gr W231, 115gr ball, oal 1.165):
Mag 1: shot all eight with lock back
Mag 2: shot seven and locked back with 8th rd still in mag
Mag 3: repeat of 2
Mag 4: stove pipe on last round with bullet facing the sky
Mag 5: shot all eight with lock back

I had different results using different ammunition. I am assuming this is probaby the cause or would it be a weak mag spring? This is the original matching mag. I guess its not that big of a deal and it won't be shot very often but I'm still curious. Appreciate any advice.

Pat

[PhilOhio]

Pat,

Although you posted this more than a month ago, it just now caught my eye. I acquired a 1937 S/42 this week and have been fine tuning it for shooting. Now and then the lock was engaging early, with rounds still in the mag. Last night I fixed the problem. The bend in the slide lock spring was such that it was slightly weak. I was able to strengthen it, without replacing the spring, but this is not always possible with springs.

For the lock to work correctly, there is a balancing act taking place. The mag spring force must be a little stronger than the slide lock spring force. If the difference is not correct, the lock will either not engage, or engage too early.

Your slide lock spring is either too strong, or the mag spring is too weak. You need to determine which one is closest to "correct" to know which one to modify or replace. To do that, you must either know, or take a guess, or replace/modify both.

If the gun is feeding reliably, the mag spring is probably O.K. Check to see if there is dirt or debris preventing the locking piece from moving up freely. You can probably feel it.

[John Sabato]

There could also be some interference from the right grip on the movement of the magazine button which causes the holdopen to do its job. Try removing the right grip and see if your problem goes away. If it does, then relieve the right grip where it touches the mag button.

[rottenII]

Gentleman, thanks for the reply. I will store your info away for a rainy day. As the pistol is all matching including the mag Ive decided NOT to shoot it anymore as to not press my luck. Hey, I figure the last mag I put through it fired all eight perfectly so I can sleep knowing it fired fine the last time I shot it right?

[PhilOhio]

John,

These holdopens look so simple, but there can be some off beat problems with them. Today I ran into a really strange new one.

I had pretty much eliminated my early holdopen problem, I thought, by correcting a weak holdopen spring. Then I began getting a premature holdopen after the seventh shot, about two out of three mags; never got it earlier. Really weird. Had to take the gun home and study that one, to see how the holdopen could possibly be actuated after round #7. It took awhile.

Turned out the original German magazine had the front part of the right feed lip bent upward only slightly too much. Feed still worked just fine, but after the seventh round was fired, the eighth round (all of them, actually) was being allowed to rise maybe .010" to .015" (a guess) too high. This allowed the follower button to sharply tap the holdopen upward only a few thousandths, but still enough so that, part of the time, it could catch the bolt;barely.

Each time it did so, all I had to do was pull and release the toggle and the last round would feed normally. This meant the holdopen spring was pulling the holdopen down to where it should have been. Strange, strange, strange.

You wouldn't think this could happen. But we have to remember how firing pins work in modern designs like the Beretta 92. The hammer only drives the rear of the pin a few thousandths before stopping against the rear of the slide face. This is a safety feature, so the pin does not rest against a primer when the hammer is down. But a full hammer impact is enough to drive, bounce, the pin very far forward against its spring and dent the primer. Apparently, the 8th cartridge in my magazine was rising fast enough under spring pressure to do something similar. Or else it was black magic.

[w2ec]

Probably not related to this original problem, but clearly related to a failure to lock open, is a situation I encountered with my newly acquired 1920 Commercial 30 Luger.

What I found is that the retainer pin on the follower button on my mag appears to be slightly too long. When the button is fully seated into the follower, there is still a significant gap between the button and the magazine body itself. The button is not flush, or even close to being flush, with the mag body. So when the magazine is inserted, the hold open lever actually fits into the space between the magazine body and the button, rather than contacting the top of the button and being pressed upwards to hold open the toggle. Short of machining the pin to shorten it, I don't see how to resolve the problem using the existing parts.

I'm also having other problems with this mag (weak spring, rough movement) so I've ordered some MecGars to use for shooting and will just keep the bad mag aside since it appears to be original to my Luger.

[Mauser George]

Pat:

I suggest you sell me this shooter Luger since it is defective!

Regards,

George

[rottenII]

Originally Posted by Mauser George

Pat:

I suggest you sell me this shooter Luger since it is defective!

Regards,

George

You are a true friend George!

[Lugerdoc]

W2, Sounds like your follower button is loose and need to be reinstalled correctly. PhilO, your fix on the HO spring was just temporary and is locking on recoil. TH

[PhilOhio]

Tom,

No, I don't think it was locking in recoil, although I have had that happen with other guns. Every premature holdopen was after ejection of round #7 in the mag; i.e., with one round remaining and the follower button extremely close to the holdopen piece. And holdopen spring tension was actually not even so bad before I stiffened it.

When I tried a mag from my artillery, there was no problem.

Since I adjusted holdopen spring pressure to be the same as on my other two Lugers, and also carefully tweaked the mag lips to match my other original mags in cartridge positioning, I have not had one of these premature holdopens in several hundred rounds. I think the lips were the main problem. With the rolled seam running up both sides of the body, adjusting the lips is tricky.


In that regard, though, I have to agree with those who say that the true fix for any Luger original magazine problem seems to be these Italian Mec-Gar mags. The design lets the lips do a better job of positioning the cartridge correctly, and their springs are fine.

[maytag]

So what is the problem when the gun fails to lock back even when you are using Mec-Gar magazines?

[RJS]

Mec-Gars are great magazines! I have 3 Beretta 92s and those mags are state of the art. In my Lugers, these perform flawlessly.

[Lugerdoc]

Maytag, I can think of 4 possibilies: YOur gun may be a pre-1914 that doesn't have a HO or your breech block is an early one, without the HO cut on bottom. Your HO may be sticking in the frame or your right grip is interfering with the movement of the follower button. TH

[FNorm]

Great discussion, very educational. Thanks, All.

FN

[Vlim]

I've been shooting 124gr S&B FMJ for years in my 1937 S/42 with DDR barrel. Holdopen always worked as it should.

I ran into a batch of 115gr Winchester whitebox which I'm shooting at the moment.
Holdopen now rarely works

[maytag]

Thank you Luger Doc (Tom) for your suggestions. My gun is a 1938 S/42 and it doesn't have an old breechlock either, so it can't be that. I'll see if the grip is interfering though. Thanks again for your input everybody!