Thanks to everyone for your sound comments (especially Dave - sorry I didn't mean for you to start measuring your receivers and toiling away in Photoshop Saturday night)! Very helpful information from all and I sure appreciate the advice.
I should add more information concerning this "problem". I've owned the Luger in question over 30 years putting thousands of rounds through it. With good ammo it's been extremely reliable.
This is a mixed parts shooter, DWM frame & toggle assembly but a 1938 Mauser barrel/receiver. Recently I got a 1913 DWM barrel/receiver and that's when I noticed how much smoother and easier the toggle moved in it than in the Mauser receiver. On the firing range both receivers work fine so as has been pointed out this really isn't a problem, other than the extra friction and wear and tear.
Anyway, I plan to get an S/42 toggle assembly and will see how its breechblock works in the 1938 receiver. (Probably no change of course.) Since it's hard for most people to tell the frame is WWI vintage, I hope to end up with a shooter that can become WWI or WWII with a swap of the upper section. In effect a poor man's way to have two shooters.
This may seem stupid, why not just sell the mixed parts pistol and buy two shooters, but I've owned this Frankenstein so long I'd like to hang on to the parts now. At the time I was a dumb kid looking at Lugers and stumbled across this one in a pawn shop. As I compared what was for sale in town I kept coming back to look at this one. It was the cheapest and ugliest but looking at the parts it was obvious there was little wear from shooting, just careless handling over the years.
I must have been one of the few people interested in it because the guy dropped the price to $100 and I couldn't walk away. I couldn't believe it when I took it out in the desert and it gobbled up 50 rounds with no jams! So there is sentimental attachment and I want to hang on to the gun. Twenty years later I did get a second Luger, an excellent all matching 41 byf that's too nice to shoot so of course the ugly one is much more fun! Took it out yesterday with my son in law and had a great time. (No he wasn't the target.

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