Light primer strike

[Lawdog613]

I reloaded 7mm-08 and shot them in a Thompson Encore pistol. I had one that did not fire. It looks like a light hit on the primer. All rounds shot previously with this frame and barrel fired fine (about 30). Primer looks to be seated fine. Any ideas of what the cause might be?

[Luckyducker]

I would be suspect of your sizing die adjustment, as it sounds like the case is being sized too short for chamber length which makes a long reach for the firing pin to reach the primer.  This seems to be more of a problem for break action rifles than for turn bolts.  You could do a test to see if this is the problem you are having,  if you can deprime a fired case without sizing it then seat a new primer in and fire the primer in your T/C and compare it to a fired case to see if you get a better primer dent in the test case.

[Lawdog613]

The cases I used where new.

[Grumulkin]

There is an Allen headed screw under where the hammer strikes the frame.  If that is loose, it will cause the problem you describe.  It could also be a weak hammer spring.  In addition, it could be excess headspace.  If the latter is the problem, it will be solved once you've shot and then sized cases to fit your chamber.

[luckydawg13]

i had a 12ga side by side do the same thing i had a lot of oil gum up fireing pin