Test firing my 1937 S/42
 

I’m going to run a magazine through my early S/42 , I’ve replaced the original matching numbered firing pin with an original backup as I’ve heard the strength of the metallurgy changes with age? Suggestions? Lighter loaded Ammo? Grains ? 115? Thoughts? Thanks Jim (also my AC41 P.38)

I think the firing pin would be the least of my worries of breaking any part. Me, it would be the ejector.

... and, yes 115gr FMJ "target loads" are best.
Winchester or PPU if you can find them.
Avoid high powered "P+" or "NATO" ammunition.

Which Ammo
 

Thanks , I do have the 124 grain modest load Blazer brass @1090 FPS ?

The Blazer brass would be my recommendation if you don't have the ability to make reduced power reloads.

It is possibly the new WWB. Lots of people are having problems with WWB these days, myself included. It is now made both in the U.S. and Bosnia. Running it through my chronograph revealed a 200 fps velocity standard deviation. And it's now referred to as "Training Ammo", printed on the box as such. The Blazer Brass is better IMHO, and priced about the same.

Regardless, either brand with 115 grain bullets will put a bit less recoil stress on the pistol than 124 grainers. There are people who will say they shoot full bore loads through their P.08's and have done so for years with no bad results. I'm an abundance of caution kinda guy and can reload reduced power rounds, so I do. I shoot steel plates at 25 yards at about 750 fps and I have noted that the plates can't tell any difference at all. Ditto for paper targets.

All the above caveats absolutely apply to your P.38, perhaps even more so, as I have seen more broken parts on WW2 P.38's than P.08's, which is why so many people suggest buying a post-war P1 for regular range shooting.

If your 1937 P.08 is a collectible, then running a couple of magazines through it should be OK to verify function, but if you want a Luger to shoot regularly then you would be better off buying a "shooter grade" in the $1,000-$1,200 price range as opposed to taking a similar value hit on your 1937 Luger should you break a serial numbered part. Just my 2 cents worth. Differing opinions may be forthcoming.
-Bob

On the surface that load is almost identical to the WW1 German military load which was a 123 grain bullet at approximately 1090 fps. Depending upon the powder burn rate, it should work well. If you have any doubts, use the Winchester 115 grain loads.

My shooter (with one side full of "road rash" from holster storage is a 1937 Mauser.

But it still is a lottery. Every shot fired could be the last one for a numbered part.

A mismatched shooter grade luger shoots the same as a high value investment gun.

On my matching number "42" 1939, which I shoot fairly regularly, I've replaced the numbered:

1. Firing pin
2. Holdback
3. Extractor
4. Breechblock

Somewhere around $200 in parts. I did not replace the matching-number toggle links, so there's risk there.

I don't think the ejector is serialized. Wasn't on my 1939.

IMO, shooter-grade Lugers are much more uncommon than matching-numbers Lugers. Perhaps a lot of forced-matching going on?