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Lets play guess the diameter...

No sense in even guessing sir, when it's that ridiculous!!! Now tell us the diameter of the firing pin as it was please......nothing like a firing pin that flops around like a clubbed fish when you are trying to shoot accurately!!!
Its pictured above .086
 
Thanks BC'z. Sorry that wasn't clear.

This firing pin as found was .078 diameter in a .086 hole. I'm sure the guy was having some cratering. There was some damage to the end of the pin, probably from the brass pinching between the pin and the wall of the hole. The issues machined off. Pin is now .059. Hole is .060. I'll post photos of the "as left" later or tomorrow. --Jerry
 
OK. msinc. I see your point and you've mostly answered the bonus question. The fit is not nearly as important as the diameter. Once the brass starts extruding/cratering it can push the firing pin up. With a 50,000 cartridge pressure, the force pushing the primer brass through a .086" hole is 290 lbs. It can push the fring pin back into the hole since that is much stronger than the spring.

Now a good firing pin fit is better for a couple of reasons:

1. Keep dirt etc out.
2. The firing pin hole is the key for cratering/piercing but for durability, the firing pin should be as large as possible and still fit i the hole. I don't like to go below .058 for firing pin diameter so the tightest fit gets me the tightest hole.
3. If you do get cratering, which is very unlikely with a ,060 hole, the tight fit will prevent brass getting pinched in the gap.

--Jerry
 
OK. msinc. I see your point and you've mostly answered the bonus question. The fit is not nearly as important as the diameter. Once the brass starts extruding/cratering it can push the firing pin up. With a 50,000 cartridge pressure, the force pushing the primer brass through a .086" hole is 290 lbs. It can push the fring pin back into the hole since that is much stronger than the spring.

Now a good firing pin fit is better for a couple of reasons:

1. Keep dirt etc out.
2. The firing pin hole is the key for cratering/piercing but for durability, the firing pin should be as large as possible and still fit i the hole. I don't like to go below .058 for firing pin diameter so the tightest fit gets me the tightest hole.
3. If you do get cratering, which is very unlikely with a ,060 hole, the tight fit will prevent brass getting pinched in the gap.

--Jerry
Does this also apply if the rifle will never see srp brass?
 
Yes, SRP vs LRP is very little difference. LRP is slightly thicker and you can get buy sometimes when your situation is borderline. But I'm bushing more bolts for guys shooting LRP brass now than SRP. --Jerry
 
Yes, SRP vs LRP is very little difference. LRP is slightly thicker and you can get buy sometimes when your situation is borderline. But I'm bushing more bolts for guys shooting LRP brass now than SRP. --Jerry
Good to know I now have a plan.
I can't wait!
 

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