Hello everyone! I have an aluminum framed post war Walther P38 stamped 12/61. I just acquired a new in the wrapper/completely stripped slide, its an 11/81 "fat slide" version. Was just wondering for future reference and possible use, is everything inside the old '61 slide interchangeable with the newer '81 slide. I have heard of the old thin slides cracking with use of hot ammo. Im not planing on shooting anything but mild reloads. I also prolly wont be shooting it that much either. But I think its always nice to have parts around just in case something should happen.

Parts should be the same, IMO. I've never read anything different.

Slides cracking, bbl retaining pin/latch (can't remember the name) would also crack, usually due to not changing the recoil springs.

My advice is worth exactly what you paid for it........................    

About the only real difference between the post-war P-38 and P1 is the stamp on the slide.
The internal parts are all the same, and most frames, slides, and barrels interchange no matter whether they have the reinforced slide or not.
Most parts will also interchange with the P4.
In fact, many WWII parts can interchange.

The situation with the P-38 and P1 is similar to the USGI Model 1911 pistols and the Colt Government Model.
The actual guns are the same, just that one was made for the government, the other was a commercial model.

I had several P38s with cracked slides and all parts from the original gun did fit the new slide with the exception of the locking block, the locking block may need fitting.