Quote Originally Posted by Wildcat View Post
I have put a lot of rounds through a GP-100.
I fought with the DA for quite a while and eventually tried using a Wilson spring kit but the gun's overly stout firing-pin spring turned out to be an obstacle.
The firing-pin is captured in the frame with a cross pin that is blended to the frame. Its designed not to be removed. (I think the newer revisions are captured by a removable bushing)
If I had a mill I could square up one end of the retaining pin and drive it out of the frame but making it look nice again would be a challenge.

Convinced I reached the limit, the best I could get to work was a 10lb trigger return spring and a 12 lb mainspring that I then shimmed to achieve reliability. Now the DA is not awesome but I'd call it reasonable. No failures in the last 2k rounds since I made the changes. This is with various factory ammo and/or Winchester primered reloads.

The good points are:
the GP-100 handles 357s very well and accurately.
The cylinder notches don't peen even if you run the gun with 1/4 sec splits. I assume this is due to the offset notch geometry.

This was a new gun in 1996.
If you look at a new one now, check to see how the firing-pin is retained. If it can easily be accessed to replace the firing-pin-spring, you should have a reasonable chance of improving the DA trigger pull.

After messing with the GP-100, I bought several used S&W revolvers.
IIRC, S&W tried several different design changes to cope with the fouling that accumulates where the cylinder turns on the yoke. Depending on whether the gas ring is part of the cylinder or whether it is on the yoke and how the gas ring is mounted in the cylinder apparently makes a difference. Somewhere around engineering change "-4" they got it sorted out.
Simply by dumb luck, my 19 and 64 are -5 and I have not had the fouling issue you describe.
Thanks for relaying your experiences.

When it "gummed up" I had been mild .38's BNH 12 and warm (@915 fps) 187 gr .357 BNH 18 double grease ring bullets. I fired a newer Colt King Cobra with the same ammo. Even more in fact, and it never slowed down.

There was no barrel leading.