I have a 625JM, installed a Wolff reduced power mainspring. I will only fire 100% w/Federal primers. I've ordered a new spring and strain screw from Brownells. I'm going to experiment with them. I'm looking for tips from anyone who has had experience in this area. I've had good luck with the wolff spring in a 686 revolver, it fires with any primer but the 625 is a different animal. I'm thinking something between the factory setup and the Wolff.
It's too bad Federal can't supply primers. I'm hoping to eliminate the need for Federal.
In addition to playing with springs to get things balanced to your liking, you may want to consider a slightly longer firing pin. The pins S&W installs are a little short to prevent accidental firing during drop tests mandated by CA. I like Cylinder and Slide shop extended pins. They are only .015” longer, but they help to ensure reliable firing in my guns. Others also make the longer pins as well.
I failed to mention that I have a C&S pin in the gun. I think I'll have to play with the new spring and strain screw. Polish the hammer lock as it rubs the side of the hammer.
If you already have a long firing pin, play with the mainspring to get the ignition reliability you want, then try a lighter rebound spring. It will have a significant impact on the double action trigger weight, while maintaining ignition with the full power or nearly full power mainspring.
I used the C&S firing pin and had pierced primers. It isn't needed.
Polish the sufaces that rub, but be careful not to remove the flash hardening from the MIM parts.
Replace the rebound spring with a Wolff 15lb unit and recurve the factory mainspring at the hooked end. You will end up with a trigger that will set off CCI primers and it will be smoother.
Thanks for the suggestions. I was successful by using the new spring and strain screw from Brownells along with a small pistol primer cup on the end of the strain screw. Note that the full power Brownell spring wasn't much stronger than the reduced power spring I got from Wolff. (The Brownell is also a Wolff spring).
I also load the moonclips with the flat side toward the breech face. Fires Rem. and Win. primers. I haven't tried CCI.
The action is smooth and much lighter than from S&W.