[eagle7373]

This (lengthy) post is my effort to contribute some things to the forum I’ve learned about the delicate balance between Luger pistols, magazines and ammunition. Most of my visits to the forum are to read and learn from others, but I think everyone should periodically add something for others to chew on and debate. Of course, when you do that, others will second guess, correct, opine, etc. That’s okay… it’s how we learn. There is also a risk that my post is “old news” and I just haven’t figured that out yet. But I hope this post will stimulate an exchange of views and I can learn something.

Disclaimer: I have included some hand load data below. These loads work for me, in my pistols, but may be unsafe for you, in your pistols. Take it for what it is worth… a data point. The final decision on what you put in your hand loads is yours alone. I take no responsibility for it.

Background: I have three Lugers. All are “collectables”, but none are terribly rare or expensive, and I feel okay with shooting them with moderate to minimal risk, as long as I take some measures to substitute parts for the numbered parts that are most likely to break. (That’s another story entirely… see the FAQs.) So I set about finding the right ammo to ensure functioning while avoiding unnecessary wear to the pistols.

The three Lugers are:
(1) 1940 Code 42 Mauser, 9mm, with non-matching (but proper) Type 3 solid body, 122 e/37 mag.
(2) DWM Alphabet Commercial, 7.65mm, with non-matching, numbered, non-blue wrap-around wood-base mag.
(3) 1946 Swiss 06/29 Commercial, 7.65mm, with two proper 06/29 Swiss mags.
(If anyone wants more data on these Lugers, see my three “just bought it” postings over the last few months).

To avoid wearing out or breaking the original mags, I bought four Mec-Gar mags. I did shoot the original mags to verify they work, but I plan to retire them and use the Mec-Gar mags only (And yes, I understand that the type 3 solid body mag and the two Swiss mags are very durable and could probably be used routinely without risk, but I still plan to put them aside.) So I used a total of eight mags over the last couple of months to get my data. I shot a couple of hundred rounds of ammo, different loads.

Early in the process I discovered that my 1940 9mm Mauser is somewhat “stiffer” than my other more modern 9mm pistols. I had developed a hand load that I always use for my CZ 85, CZ75, and Ruger LC9 that is a mild target load and reduces wear on the shooter and the pistols. It is 4.0 grains of Bullseye with a Rainer 115gr JHP bullet at OAL: 1.085” . When I used factory ammo in my Mauser Luger it worked fine (with both the original and Mec-Gar mags), but the mild hand load stove-piped about 30% of the time. When I bumped up the load to 4.2 grains of Bullseye, it worked fine.

Another interesting thing I discovered early was that my Swiss Luger worked fine with both the PPU and Fiocchi 7.65mm factory ammo and the Swiss mags, but would not latch back after the last round when using the Mec-Gar mags. Huh? Mec-Gar mags are supposed to be the gold standard. As for the DWM Commercial, it too worked with both brands of 7.65mm factory ammo, when using the original mag and the Mec-Gar mags, although the wraparound mag had a couple of failures to feed. Mec-Gar was fine.

So I knew the hold open is actuated by the mag button, which depends on spring strength. I figured I needed more spring strength, so I ordered some Wolff springs. These are advertised as “plus 10%.” When they came in I changed out all four Mec-Gar mags. (A mistake, in hindsight).

Meanwhile, I had obtained some Lee dies and some Hornady 90 gr .309 XTP JHP bullets, which is almost the only viable bullet option handloaders have for 7.65 Parabellum in the U.S. I developed three “mild to medium” 7.65mm loads:

- 4.0 grains of Bullseye, Hornady 90 gr XTP, OAL: 1.135”
- 4.2 grains of Titegroup, Hornady 90 gr XTP, OAL: 1.135”
- 4.6 grains of Unique, Hornady 90 gr XTP, OAL: 1.135”

My goal here is to have loads that function the pistol, but do not slam the slide back against the frame too hard, to avoid excessive wear. (By the way, the factory ammo does this. The PPU is very strong, and the Fiocci is not quite as bad, but is still strong).

So I took both 7.65 pistols back to the range and fired them using all the loads. The big surprise was that, while the Mec-Gar mags with Wolff springs were now better for the Swiss Luger (reliable functioning and latch back after last round, most of the time), they were too strong for the DWM Commercial. The pistol functioned fine on the first few rounds of a mag, then, would latch open with one or two rounds still in the mag. For both pistols I verified that the first two hand loads worked fine, except for the same latching problem after the last round. The Unique load worked in the Swiss, but occasionally stove-piped in the DWM Commercial. I attribute this to the longer barrel of the Swiss, which allows more “back pressure’ to function the action. For the DWM Commercial, I needed to bump it up to 4.7 grains of Unique.

I realized I had been looking at the wrong solution for the latching problem. After more work it became apparent that the problem was the hold-open itself. In the DWM Commercial the hold-open was “looser” and moved very easily. That meant the strong Wolff spring in the Mac-Gar mag pushed the latch into position too quickly and latched the toggle open before the mag was empty. In the Swiss, which is essentially a new pistol, the hold-open was a bit tight and “dragged” a little. This meant that it could not move fast enough to put the latch into position after the mag was empty, so the toggle did not latch open.

I took out the Swiss hold-open, dressed it up by polishing the sides, and reinstalled. Now the Mec-Gar mags with Wolff springs work with both factory and hand loads. I took the springs out of two of the four Mec-Gar mags, replaced them with Mec-Gar springs, and these now work fine in the DWM Commercial. The Swiss hold-open still needs work, as it does not yet reliably latch open when using the Mec-Gar mags with Mec-Gar springs.

So what did I learn?

1. The balance between mags, ammo and operability can vary from one Luger pistol to another, based on individual components.

2. The functioning of a Luger requires just the right amount of “back pressure” to move the slide back hard enough, but not too hard, to allow the components to work together.

3. Mec-Gar mags are pretty darn good and work well for most pistols, but it is possible that you may need either a stronger or weaker spring in your pistol. In other words, stronger springs are not always better, though you often hear this.

4. The Luger design requires a certain minimum amount of power to function it. When hand loading, you have to make sure you have enough powder to drive the slide, but not too much to slam it into the back frame and deface the surfaces.

5. Don’t assume your hand-fitted pistol is perfectly tuned. In my case, I had a sticky hold-open on a “like new” pistol. I have improved it, to the point I can use it with extra strong mag springs, or with the Swiss mags (which have strong springs), but I still need to work on this part so I can use regular Mec-Gar mags.

There may be other lessons I can squeeze out of this. I’m also interested in learning from the experience of others and hope this will get a conversation going. Anybody else have pet hand loads to share? Any other tips on Luger tune-ups? Any other thoughts on magazines? I know there may be other previous posts on this topic, with information I have not yet discovered, but I hope this is useful to others.