Cooper Model 52 Misfire Problem

[JayCutright]

I have a Cooper 52 in 25-06 that misfires about 1 out of 5 rounds, the primer shows a light strike but no bang not even if i attempt to fire the same round twice. The rifle has a pin protrusion of .108 which is very excessive unless Cooper somehow wants it that way. There’s no binding the firing pin the spring is stout and everything works fine on all but a few rounds from each box, what could be causing this?

 

[Carl S]

To much pin protrusion .055-.060 is ideal.no binding or drag and pin falls as it should.may be the spring is a little weak.check primer seating depth.may be a bad batch of primers-ammo if factory loaded.

 

[Ggmac]

excessive headspace ? Factory ammo ? Possible resizing issue ? Bad lot of primers ? Need more info.

 

[JayCutright]

Headspace is right, two different brands of factory ammo

 

[swd]

Have you taken the firing pin assembly out of the bolt and checked for an old blanked primer cup or garbage and cleaned and checked everything?

 

[JayCutright]

Have you taken the firing pin assembly out of the bolt and checked for an old blanked primer cup or garbage and cleaned and checked everything?

Yes

 

[swd]

Yes

Then I’d try a new spring at this point.

 

[JayCutright]

Then I’d try a new spring at this point.

I am going to shorten up the firing pin protrusion to .060 and see what that does, I’m not sure where I would find a replacement firing pin spring for a Cooper nowadays.

 

[JayCutright]

I set up my tool post grinder and shortened the firing pin to .057 protrusion and so far it hasn’t miss fired in 15 shots of two different brands of ammo, I knew .108 pin protrusion was to much but I wasn’t convinced that was causing the misfire, I just reworked the firing pin as a process of elimination to get to the root of the real problem and found the protrusion was the problem after all.