Firing pin tip shape

R

Rflshootr

Member
Is there a proper radius size for a firing pin tip? From what I remember, it isn't suppose to be a complete radius (half ball shape) but a larger radius then half the tip diameter.
 
Recently, I have started shaping the firing pin tip to kind of a cone with a radius. This for larger pins (like the post 64 Model 70). I started doing this in an attempt to prevent blanking without bushing the firing pin hole. It seems to work. The cone commences at the bolt face (with the pin protruding) and tapers down to 1/16 inch about .030 from the end. Regards, Bill.
 
Bill Leeper said:
Recently, I have started shaping the firing pin tip to kind of a cone with a radius. This for larger pins (like the post 64 Model 70). I started doing this in an attempt to prevent blanking without bushing the firing pin hole. It seems to work. The cone commences at the bolt face (with the pin protruding) and tapers down to 1/16 inch about .030 from the end. Regards, Bill.
Click to expand...

Hey! That's not bad!

I'da' never thought of it but in retrospect the stretched cone is much stronger, takes gas impingement better and virtually eliminates the stress riser and fatigue generated by the typical forward/back folding action of the typical garbage-can-lid blank.....you could actually "pierce" a primer with your arrangement and it'd self-heal LOL!!!
 
When a cartridge is fired, do you think that the firing pin reaches its full extension from the bolt face? Perhaps the issue is how far back the shape extends before it reaches the maximum diameter. Just a thought...
 
Was a time when the recommendation was a flat face and a radius around ¼ pin diameter, but I recall that design was to still hit the primer anvil while compensating for the tolerances in manufacture.
 
Boyd Allen said:
When a cartridge is fired, do you think that the firing pin reaches its full extension from the bolt face? Perhaps the issue is how far back the shape extends before it reaches the maximum diameter. Just a thought...
Click to expand...

Well.... I have a lot of Remingtons and I will be trying the cone-shaped tip I think :)
 
I had severe blanking with a newer M70 and a 6x47 Lapua (srp). With mild starting loads it still blanked primers. The radius on that firing pin tip did in fact retreat too far into the bolt face when firing and sheared perfect circles out of 90% of the primers fired. I ended up bushing it and turning down to .067” or so and never a problem afterwards.
 
I had a discussion with Ed Shilen about tip shape back in the 80's. What he said made sense. Flat with a very small radius on the edges which reduces cratering and helps reduce piercing.
 
msalm said:
I had severe blanking with a newer M70 and a 6x47 Lapua (srp). With mild starting loads it still blanked primers. The radius on that firing pin tip did in fact retreat too far into the bolt face when firing and sheared perfect circles out of 90% of the primers fired. I ended up bushing it and turning down to .067” or so and never a problem afterwards.
Click to expand...

I wonder how much is too much. Most actions have nominally .050-.060 protrusion and .250 pin fall. So roughly .200 pin retraction on "most" actions.
I have to say that I don't think this is what causes piercing or maybe I'm misunderstanding your post.
 
mwezell said:
I wonder how much is too much. Most actions have nominally .050-.060 protrusion and .250 pin fall. So roughly .200 pin retraction on "most" actions.
I have to say that I don't think this is what causes piercing or maybe I'm misunderstanding your post.
Click to expand...

Swap ogive for radius & it seems logical.
 
You must log in or register to reply here.
Back
Top