I've had this .357 M&P R8 (really a S&W trr8 with a few minor differences) for about 1 year now. I've shot just under 1k rounds (about 30% .38 special, 70% .357 magnum). Over the last few outings, I've noticed an increasing number of light primer strikes. It started off as a few here and there, and I could always cycle the dented primer one more time to shoot it off.

Now, it's gotten to the point where I'll have 6-9 rounds with dented primers but won't fire, no matter how many times I cycle the cylinder. The light primers are mostly happening with PPU .357 magnum 158gr...not top-of-the-line ammo, but certainly not **** ammo.

This is really quite frustrating, because that light primer strikes aside, this revolver has been fabulous to own and shoot. Anyone else here have similar experiences with their R8's or TRR8's? I'm thinking this needs to go back to S&W for fixing. I wonder if the Performance-center tuned action has anything to do with hammer strike/reliability?

New mainspring and mainspring tension screw

Did the light strikes begin only after the tuning? If so, ... that could be a problem. I assume you have checked for a tight strain screw? With less than 1K rounds fired, wear shouldn't be an issue. But PPU may have harder primers than some, don't know, but try some Federal as they may ignite easier.

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I would try some different ammo, and like Peak53 I would check the strain screw.

It sounds like the strain screw became loose. Take the grip off and see if I am correct. It should be tight against the main spring. This exact thing happened to my 686. Started getting light strikes which became progressively more frequent. Turned out it was the strain screw having come loose. Once I fixed it the gun has been 100% ever since.

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Also check for cylinder endshake

Occam's razor - tighten the strain screw. Not unusual for them to back off with use in a new gun. Maybe a drop of purple Loc-Tite to keep it from happening again.

And yes, PPU primers are harder than any domestically produced ones - just a contributory factor. Will probably be OK once the strain screw is tightened.

KISS

Adios,

Pizza Bob

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Groo here
Has your gun had the firing pin replaced with the longer one?
If not , I would consider one.
After the main spring screw .
Doubt the main spring as they should last 10's of 1k rounds.
I have never changed a worn out one in 50 years of shooting.

With all due respect, why?

IIRC the longer firing pin was only a factory fix on some of the first 625's when they changed to the frame-mounted FP and was a specific cureonly for those guns. While it is a common modification for most competition guns, it is neither necessary nor a cure-all for every "light-strike" situation, which 90% of the time is just a loose strain screw.

Adios,

Pizza Bob

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Those performance center mainsprings have failed.
If it wasn't the strain screw, I would suspect the mainspring.

If you have another revolver, you can swap out the mainspring with a regular one. The trigger will be a bit harder, but it will fire.

Those PC mainsprings are good when they work, but they have the weakest tension and can cause problems.

Update: I took off the grip and tightened the main spring strain screw. At first I only tightened it partially; test-fire still had 1 light primer strike with PPU. Then I tightened the screw until it was snug (wouldn't tighten anymore). No more light primer strikes. Is that main spring screw supposed to be tightened all the way?

Yes, yes it is.

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