Tuning for Reliability
 

I have a matching and mechanically perfect, albeit bloodstained, 1937 HK Luger that I've been trying to set up as a shooter. So far, reliability has eluded me, notwithstanding the use of Haenel-Schmeisser and MecGar magazines and Wolff springs in all weights, mostly in the form of stovepipes and failures to feed. I would be very grateful for any tuning tips or pointers to gunsmithing literature.

https://lh4.googleusercontent.com/-1...3-no/8551c.jpg

Out of my range experience (mainly with 1911 GLOCKs and CZ) I had stovepipes when my loads were too light fo the recoil spring or the recoil spring too heavy, or problems with the extractor (worn extractor hook, tension too high); I had failure to feed generally when I had faulty magazines, but could be caused also by too much extractor tension, or worse still a barrel somehow throated imroperly.

Sergio

I understand the theory, but in practice my pistol short-strokes on 115 and 124 gr Winchester White Box ammo with a 16 lbs recoil spring, as if it's asking for NATO loads that I'm reluctant to use.

It should work fine with WWBox 115 grs, at least with the original recoil spring. I'm suspecting the extractor might be the culprit.

Michael,

Check to see the condition of the inside chamber surface. If it's severely pitted or frosted from the blood splatter, it might be adding enough friction to the extraction process to put off the timing.

Use some masking tape on the rear of the receiver and look for impressions of the rear toggle hitting it. If there are no marks whatsoever there is not enough recoil force driving things back. If there is too much force (the paper is being hit hard, heavily marked or cut into) the toggle train may be bouncing back very quickly.

Double check how you are supporting the Luger during cycling. You need a firm, solid stable hand hold to oppose the frame recoil force.

Try a 21 or 22 coil recoil spring. This is what was used during later Mauser production and may apply to your HK.

Marc

The pistol is like new internally. There is nothing wrong with the chamber, the rails, or the extractor.

Hi:

Please give us a full definition of "short strokes".

I'm willing to try it again, as your 9mm should work perfectly, with relative ease.


Sieger

Let's make a simple test. Load one round and shoot it. does it lock open?

Can you see any possible flaws to the extractor claws(tips), or the breachface? Does the extractor move freely, and to it's full extent in the extractor channel?

No flaws anywhere to be seen; lock open is sporadic.

Very common to occur. It appears there's nothing wrong with the recoil spring your'e using. You may have some excessive slack in the magazines, it should be no more than 2mm at the bottom.

Nowhere near that much slack in any of the magazines. It feels like the pistol is asking for a spring lighter than 16 lbs, or NATO-spec ammo.

I would use the paper test on the rear of the frame, should be compressed but not broken, this is you optimum cycle.

Stove pipes can happen when the toggle hits the rear of the frame and bounce forward, this increase energy in turn bounces the new round up on the ramp to hard and a jam occurs.

Cycle some dummy rounds through your gun and observe how they get picked up by the breach block and how the extractor slides over the rim of the casing. A rough extractor will cause the new round to tip up as it goes up the ramp and cause a jam

The front of the extractor can be smoothed with 600 grit or higher

Just some ideas :)

Vern

This may be a dumb question, but with the stove pipes and short-stroking I have to wonder do you experience this with any of your other P.08s? If so, you may be limp-wristing it.

The only Lugers I've been able to make work are the LP08 and the 06/29. I never had any luck with the standard P08.

Michael,
Have you verified that the magazine button is not rubbing against the grip, or some other obstruction?
KFS

Mike,

Whatever method you used to make these other two Lugers "work", one of which is a 9mm, should be followed with your new project Luger; as for me, getting my LP-08 to function was a lot trickier than getting my standard model to function. By "function", I mean three shot groups touching and at least 1,000 rounds shot with no jams.

Sieger

I don't have any idea how many P08s that you have tried firing, but if it was more than a couple, and you never could get one of them to function, I would have to consider the shooter. I mean no disrespect, but a very firm grip(one or two handed) is needed to allow the recoil response to fully cycle the toggle train. A soft grip will definitely lead to multiple malfunctions. I speak from experience concerning this.

It may be something totally different than grip, but it is certainly something to consider. The longer barreled Lugers have more sliding mass, which translates to more momentum during the rearward portion of the cycle. That could be making the difference for you.

In a mechanically sound device slow to medium speed burning powder will solve all of your problems. Modern powders are too fast and snappy for P08. Off shelf ammo being loaded with very fast BR powders are not ideal food for P08s. Reason for that is to ensure proper functioning of majority carry weapons on today's USA market. Most of them have pipes less than 10 cm long. Nitrocellulose based powders from the beginning of the 20ieth century were not fast BR powders.

Then maybe you have too little slack on your magazines. Who knows.

I would't recomend the use of a lighter spring, perhaps just the opposite. If the toggle is working too fast there won't be enough time for the next round to present itself in the magazine before the breech block returns.