Firing pin face shape ?
- Thread starter jimbo_10x
- Start date
High pressure cartridges should have a flattened tip. Well, at least according to Bob Dunlap, but what does he know.
No, round, spherical, is not the ideal shape for a high pressure firing pin. Flatten, shorten, the pin a little. Your firing pin is probably too large for what you're doing. Don't leave any sharp edges. If you're not capable of doing this yourself then farm it out to a competent smith.
Bushing the firing pin hole is nice, and could help, but is not usually necessary and will not, by itself, alleviate your problem. The pin on most Remington rifles is spherical. That is not the best design for high pressure rounds. Spherical pins come to a round point and that is where high pressure rounds fail. Reduce the point on your pin so that it is not completely spherical.
Again, if you're not competent enough to do this yourself then farm it out to a gunsmith.
I’m curious what makes a flat tip better. Is there an explanation?
I have never seen a flat tip specified.
People will put in an oversized pin in hopes that it is the gap between the standard pin and the hole which is the cause of cratering. It is not.
I dislike the idea of using a flattened tip on the firing pin and believe a smooth sphere is better. A flattened tip with rounded edges is probably ok. Most primer piercing is actually blanking which is caused by a lack of support for the primer. The lack of support is made worse when the firing pin tip has a sharp edge at it's flattened tip. This edge shears the primer cup and weakens it.
Light strikers in combination with a weak spring can lead to blanking. Interestingly enough, excessive protrusion often means reduced striker travel and a lighter strike so the chance of piercing is actually not greater than it would be with proper protrusion.
I had one rifle brought in which was piercing primers. It was a Borden action which had a firing pin with a flattened tip. It had obviously been made that way. I reshaped the tip to a smooth hemisphere, losing about .004" of protrusion in the process, and it never pierced another primer. In this case the primer was piercing rather than blanking.
I have experimented with a Winchester firing pin on which the tip is shaped like a short, truncated cone with a 1/32 radiused point. The idea being that the pin might mimic the 1/16 diameter pin while avoiding the bushing of the bolt face and turning of a smaller pin tip. While it seems to work OK, a sample of two doesn't really give solid data. WH
I dislike the idea of using a flattened tip on the firing pin and believe a smooth sphere is better. A flattened tip with rounded edges is probably ok. Most primer piercing is actually blanking which is caused by a lack of support for the primer. The lack of support is made worse when the firing pin tip has a sharp edge at it's flattened tip. This edge shears the primer cup and weakens it.
Light strikers in combination with a weak spring can lead to blanking. Interestingly enough, excessive protrusion often means reduced striker travel and a lighter strike so the chance of piercing is actually not greater than it would be with proper protrusion.
I had one rifle brought in which was piercing primers. It was a Borden action which had a firing pin with a flattened tip. It had obviously been made that way. I reshaped the tip to a smooth hemisphere, losing about .004" of protrusion in the process, and it never pierced another primer. In this case the primer was piercing rather than blanking.
I have experimented with a Winchester firing pin on which the tip is shaped like a short, truncated cone with a 1/32 radiused point. The idea being that the pin might mimic the 1/16 diameter pin while avoiding the bushing of the bolt face and turning of a smaller pin tip. While it seems to work OK, a sample of two doesn't really give solid data. WH
No one said a flat tipped pin, but to flatten the tip of the pin. Lower the arc so the tip is not completely spherical. Do it in a manner that leaves no sharp edges. Unless you took two and held them side by side you would not even know it had been done. The average shooter, not a fudd mind you, I mean the average competitive shooter, would not even know because most just order their rifles built and go shoot. The benchrest community is a little different than the average competitor and most benchrest shooters would probably know if their pins were spherical or not, but i guarantee not all do.
In this case the OP specified that he had already ordered the oversize firing pin. The point of the over size pin is to occupy the excess space in the bolt face that Remington rifles are notorious for. It was suggested that he bush the firing pin hole. There is little to nothing to be gained from bushing a firing pin hole when you're already running an oversized pin. Reduce the radius and increase the striking surface of the pin is his next logical course of action.
Grind it down.
If you measure the protrusion on Remington or Remington clone bolts, they are usually in the .055 - .060 range. I have measured dozens of Defiance actions and every one of them is in this range. With a primer in, the maximum protrusion you will get is around .030. So, this means one of two things:
a. all the manufacturers are wrong and are making pins that protrude too much
b. it is designed this way and works great.
Since I have never had a single pierced primer with a Defiance action, I'm going with choice b. Custom action makers have done two things to make pierced primers a thing of the past:
1. reduced the tip diameter to .062
2. change the geometry of the pin tip to make it less likely to pierce.
For these reason, I don't think grinding a firing pin is the way to go. Protrusion doesn't matter, but you will change the tip geometry. Terry, when you grind the firing pin tip, are you maintaining the original pin geometry or are you changing it to a custom design of your own? Perhaps you are a pro and get good results. I"m not sure you should be posting that Joe Public should do the same.
a. all the manufacturers are wrong and are making pins that protrude too much
b. it is designed this way and works great.
Since I have never had a single pierced primer with a Defiance action, I'm going with choice b. Custom action makers have done two things to make pierced primers a thing of the past:
1. reduced the tip diameter to .062
2. change the geometry of the pin tip to make it less likely to pierce.
For these reason, I don't think grinding a firing pin is the way to go. Protrusion doesn't matter, but you will change the tip geometry. Terry, when you grind the firing pin tip, are you maintaining the original pin geometry or are you changing it to a custom design of your own? Perhaps you are a pro and get good results. I"m not sure you should be posting that Joe Public should do the same.
Alex Wheeler
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Round is not causing your problem. Bind/drag or trigger problems are most likely the issue with random light hits/blanking. I have also seem bad lots of primers do this. Protrusion is also not the issue unless its too little. The firing pin stops on the primer not the firing pin stop, the firing pin stop/collar only stops the pin when dry firing.
Thanks for all the comets .
I have been a machinist for 35 years so I can measure , fit ,reshape the pin accordingly.
I ordered a pin that was only oversized a small amount to take up slop in the original pin hole . I forget how much it was oversize but it was only a small amount so I don't feel the diameter is the problem . I trued the bolt faces and lugs and after doing so I researched the amount of protrusion I needed and cut the pin to that length .
Now after doing more research and listening to your coments I feet my problem may be that I have a radius on my pin that matches the pin diameter and with the high pressure 6.5x47 I feel I need a larger radius on th face . Not flat but deffinetly larger and polished edges .
Soon as i get a chance I'll shoot some more and post my results
I have been a machinist for 35 years so I can measure , fit ,reshape the pin accordingly.
I ordered a pin that was only oversized a small amount to take up slop in the original pin hole . I forget how much it was oversize but it was only a small amount so I don't feel the diameter is the problem . I trued the bolt faces and lugs and after doing so I researched the amount of protrusion I needed and cut the pin to that length .
Now after doing more research and listening to your coments I feet my problem may be that I have a radius on my pin that matches the pin diameter and with the high pressure 6.5x47 I feel I need a larger radius on th face . Not flat but deffinetly larger and polished edges .
Soon as i get a chance I'll shoot some more and post my results
Common problem with Rems, kind of hit or miss when using a 6.5x47. More likely you are blanking primers not piercing and often times fitting the pin to an original size hole wont fix it. .062 hole being smaller leaves less unsupported area under the primer and cures the problem. I've seen high end customs with large pin blank 47L primers.
https://www.bing.com/videos/search?...n&qpvt=greg+tannel+bushing+fire+pin&FORM=VDRE
https://www.bing.com/videos/search?...n&qpvt=greg+tannel+bushing+fire+pin&FORM=VDRE
Last edited:
jonbearman
I live in new york state,how unfortunate !
I had a problem with a 700 bolt and pin. So I took advice and sent it to greg Tannel and now it has been perfect for years with no not one burst primer. If you are a machinist you can probably do it yourself. This isnt our first rodeo and have been down this road many times so do the bushing job and turn down the pin to .062 and I would hedge a bet you will have zero problems in the future.
While the rifle is likely to fire just fine with less protrusion (and I am usually happy with .050) you don't want the pin to hit the shoulder when the rifle is fired. If it does, the pin is likely to bounce back and the primer loses support. Blanking may result. It can be a fine line. WH
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