Sharing in case anyone else is hunting this problem.

I decided to give competitive shooting a try this year and chose to start with revolvers (having never been a revolver shooter before.)

I've had mixed luck. On stages where both my gun and I work well I hit the top 1/3 combined divisions but the overall failure of my gun (exacerbated by my frustration) usually finishes me low overall.

For Steel Challenge I'm shooting a 627 PC and have experienced some "issues".

My choice of grips hindered reloads, the cylinder yoke falls out if I'm not very careful when reloading (apparently not an uncommon issue).

But the BIG issue has been erratic FTFs due to light hits. (Gun is stock except for grips, front sight and wolf springs)

1st I thought it was my reloads. I used the last of a case of Fiocchi primers which are known to be a little hard. So, I tried a match with Federal Factory 130gr jacketed round nose and light hit failures INCREASED.

I installed an extended firing pin, cleaned and tightened everything and went to the range on a Friday.

I fired 200 rounds without a failure.

Next day I took the gun to a Steel Challenge Match.

Again, I couldn't detonate 3 in a row.

This went on for a couple matches until I stumbled on the problem.

Though it seemed fully tightened, the strain screw (main spring) was backing itself out during firing. The timing was just right that 200-300 rounds of practice backed it out enough to cause problems at the weekend events.

I used pipe thread Teflon tape and it seems to have solved the problem. (Instead of Loctite since the strain screw is pretty tiny and I didn't want to struggle removing it in the future.)

Hope this saves someone the frustration if they experience this same intermittent issue.

Now I mostly only have myself to blame