Brushed Firing Pin

[YoteChaser]

Can someone explain the reason why you would Brush the firing pin ?
I have a firing pin that hits the primer very hard and creates a crown that I feel makes the bolt
heavy no matter the powder charge I'm shooting a 22BR
Brush the firing pin was suggested to try to fix the issue...

 

[Toms]

Can someone explain the reason why you would Brush the firing pin ?
I have a firing pin that hits the primer very hard and creates a crown that I feel makes the bolt
heavy no matter the powder charge I'm shooting a 22BR
Brush the firing pin was suggested to try to fix the issue...

You bush the bolt face and use a smaller diameter pin with little clearance around it. The crown you talk is from too much gap around the pin. It's called blanking primer. Hot loads can cause but I never had it happen with a bushed bolt. Toms

 

[Coyotefurharvester]

1. Easier bolt lift
2. Firing pin will be centered on primer
3. No more primer crater, so you can actually use primer appearance to judge pressure.

 

[SSL]

I believe you mean 'bushing' the firing pin? Bushing, as I understand it, provides a closer fit of the pin to the bolt. This helps mitigate the 'cratering' that can occur when there is a substantial gap between the pin and the sides of the hole in the bolt. It will NOT, however, eliminate such cratering due to excessive loads.

 

[YoteChaser]

You bush the bolt face and use a smaller diameter pin with little clearance around it. The crown you talk is from too much gap around the pin. It's called blanking primer. Hot loads can cause but I never had it happen with a bushed bolt. Toms

Thanks Tom

 

[YoteChaser]

1. Easier bolt lift
2. Firing pin will be centered on primer
3. No more primer crater, so you can actually use primer appearance to judge pressure.

Thanks this helps....

 

[YoteChaser]

I believe you mean 'bushing' the firing pin? Bushing, as I understand it, provides a closer fit of the pin to the bolt. This helps mitigate the 'cratering' that can occur when there is a substantial gap between the pin and the sides of the hole in the bolt. It will NOT, however, eliminate such cratering due to excessive loads.

Thanks SSL

 

[swd]

If there’s too much slop around the pin that little crater can get blown out and end up back inside the bolt. It’s called blanking a primer. And if you’re using a Jewel trigger that condition is notorious for breaking a part inside them when the pin gets jammed back. Bushing the bolt/pin has no downside and is relatively cheap $100-$120.

 

[YoteChaser]

If there’s too much slop around the pin that little crater can get blown out and end up back inside the bolt. It’s called blanking a primer. And if you’re using a Jewel trigger that condition is notorious for breaking a part inside them when the pin gets jammed back. Bushing the bolt/pin has no downside and is relatively cheap $100-$120.

Thanks SWD

 

[Will Henry]

The cratering, or blanking, is not caused so much by the gap around the firing pin as it is by the size of the hole; this regardless of firing pin fit. There are other factors as well. A large hole of say .80" is likely to result in blanked primers at high pressure; even with a firing pin diameter of .0795. This because there is enough area for the pressure to act upon that it exceeds the ability of the primer cup to withstand the pressure. Now, if the firing pin is heavy enough, there may be enough inertia to support the cup adequately and prevent the blanking but the extra weight increases lock time, so there is a tradeoff there. If the boltface is bushed and the hole diameter reduced to .0625", the area upon which the pressure acts is nearly halved. This means there is only half as much pressure acting on the cup, which can easily withstand the reduced stress, even if there is a gap.
Firing pin tip shape can also influence the ability of the primer to with stand pressure. A hemispherical tip is easy on the material but offers a full diameter area for the pressure to act upon. A firing pin tip in the shape of a truncated cone with a rounded tip, providing the cone is fully outside the bolt face when fired, may serve to provide a stronger indentation of the primer, just due to the shape.
The depth to which the firing pin indents the cup also has an effect.
So, the bushing of the bolt face, along with the reduction in firing pin diameter will absolutely end blanking or cratering of the primer and will allow one to load to higher pressures. This is not necessarily because the fit of the pin to the hole is better; it is simply because the area of the primer which is unsupported is reduced. WH

 

[YoteChaser]

The cratering, or blanking, is not caused so much by the gap around the firing pin as it is by the size of the hole; this regardless of firing pin fit. There are other factors as well. A large hole of say .80" is likely to result in blanked primers at high pressure; even with a firing pin diameter of .0795. This because there is enough area for the pressure to act upon that it exceeds the ability of the primer cup to withstand the pressure. Now, if the firing pin is heavy enough, there may be enough inertia to support the cup adequately and prevent the blanking but the extra weight increases lock time, so there is a tradeoff there. If the boltface is bushed and the hole diameter reduced to .0625", the area upon which the pressure acts is nearly halved. This means there is only half as much pressure acting on the cup, which can easily withstand the reduced stress, even if there is a gap.
Firing pin tip shape can also influence the ability of the primer to with stand pressure. A hemispherical tip is easy on the material but offers a full diameter area for the pressure to act upon. A firing pin tip in the shape of a truncated cone with a rounded tip, providing the cone is fully outside the bolt face when fired, may serve to provide a stronger indentation of the primer, just due to the shape.
The depth to which the firing pin indents the cup also has an effect.
So, the bushing of the bolt face, along with the reduction in firing pin diameter will absolutely end blanking or cratering of the primer and will allow one to load to higher pressures. This is not necessarily because the fit of the pin to the hole is better; it is simply because the area of the primer which is unsupported is reduced. WH

Wow Thanks for the explanation Will Henry... looks like I'm having the bolt face brushed...

 

[wedgy]

Paul at Pro Precision does excellent work and quick turn around time for bolt bushing.

Home

Post in thread 'Shout out to Boltfluter!'

Friday at 1:14 PM

Paul is the man no doubt. My "Smith" @ ODCR has him do all of his fluting. Perfect work on all of my stuff.

That speaks volumes!

• JLT

• 

 

[YoteChaser]

Paul at Pro Precision does excellent work and quick turn around time for bolt bushing.

Home

Post in thread 'Shout out to Boltfluter!'

Friday at 1:14 PM

Paul is the man no doubt. My "Smith" @ ODCR has him do all of his fluting. Perfect work on all of my stuff.

That speaks volumes!

• JLT

• 

Thanks for the guidance and referral Wedgy...

 

[VA_XTC_Shooter]

The cratering, or blanking, is not caused so much by the gap around the firing pin as it is by the size of the hole; this regardless of firing pin fit. There are other factors as well. A large hole of say .80" is likely to result in blanked primers at high pressure; even with a firing pin diameter of .0795. This because there is enough area for the pressure to act upon that it exceeds the ability of the primer cup to withstand the pressure. Now, if the firing pin is heavy enough, there may be enough inertia to support the cup adequately and prevent the blanking but the extra weight increases lock time, so there is a tradeoff there. If the boltface is bushed and the hole diameter reduced to .0625", the area upon which the pressure acts is nearly halved. This means there is only half as much pressure acting on the cup, which can easily withstand the reduced stress, even if there is a gap.
Firing pin tip shape can also influence the ability of the primer to with stand pressure. A hemispherical tip is easy on the material but offers a full diameter area for the pressure to act upon. A firing pin tip in the shape of a truncated cone with a rounded tip, providing the cone is fully outside the bolt face when fired, may serve to provide a stronger indentation of the primer, just due to the shape.
The depth to which the firing pin indents the cup also has an effect.
So, the bushing of the bolt face, along with the reduction in firing pin diameter will absolutely end blanking or cratering of the primer and will allow one to load to higher pressures. This is not necessarily because the fit of the pin to the hole is better; it is simply because the area of the primer which is unsupported is reduced. WH

Has anyone looked at smaller diameter firing pins than 0.062? I am wondering if reducing FP hole even further has benefit? I would suspect firing pin integrity is one limiting factor. Just curious why not say 0.050?

 

[BoydAllen]

First of all, I have considerable experience with a firing pin with a .062 tip diameter. I have shot a Stiller Viper action that has one, for many years, and really like this feature, but, if your firing pin hole edges are nice and square you may solve a cratering problem without bushing the bolt face. A friend has a couple of Panda actioned short range benchrest rifles that he shoots with loads that are very stout. Not wanting to have his bolt face damaged by primer failure, and seeing a small amount of cratering, given that his firing pin fit is good, he shimmed his firing pin spring and the problem went away, even with the very stout load. He has a lathe so this sort of thing is easy for him to do. Years ago someone mentioned, in an article in Precision Shooting, that the proper shape for a Remington 700 pin tip has two radii, a larger one in the center and smaller at the edges. A change to this shape is not difficult if needed. With a hemispherical tip, under peak pressure, the pin is pushed back a bit so that the full diameter of the tip goes below the bolt face a bit, leaving a wedge shape space around the edge, providing room for the primer cup to be cratered. With a flatter shape this is less of an issue. Not many know that there are a couple of sources for firing pins that come with oversized tips that are designed to be fitted to a close fit to the hole. I believe that one is Pacific Tool and Gauge, and the other is Holland Shooters Supply. Many hears back I had one from Holland, from a review that I had written, and I gave it to a friend who had a cratering problem with one of his 700 varmint rifles. He fitted it, and it solved his problem. Getting back to my Viper, it has been my experience that I can get away with a lighter firing pin spring with its tip diameter, with no accuracy issues. If you have an issue wiht a larger tip diameter the first two things that I would suggest you do is to check the weight of your spring, and take a look at the tip shape.

 

[swd]

.062” seem to solve the problems so I can’t see any advantage to going smaller. It’s just not needed. And at some point your going to start poking holes if it gets too small .

 

[YoteChaser]

First of all, I have considerable experience with a firing pin with a .062 tip diameter. I have shot a Stiller Viper action that has one, for many years, and really like this feature, but, if your firing pin hole edges are nice and square you may solve a cratering problem without bushing the bolt face. A friend has a couple of Panda actioned short range benchrest rifles that he shoots with loads that are very stout. Not wanting to have his bolt face damaged by primer failure, and seeing a small amount of cratering, given that his firing pin fit is good, he shimmed his firing pin spring and the problem went away, even with the very stout load. He has a lathe so this sort of thing is easy for him to do. Years ago someone mentioned, in an article in Precision Shooting, that the proper shape for a Remington 700 pin tip has two radii, a larger one in the center and smaller at the edges. A change to this shape is not difficult if needed. With a hemispherical tip, under peak pressure, the pin is pushed back a bit so that the full diameter of the tip goes below the bolt face a bit, leaving a wedge shape space around the edge, providing room for the primer cup to be cratered. With a flatter shape this is less of an issue. Not many know that there are a couple of sources for firing pins that come with oversized tips that are designed to be fitted to a close fit to the hole. I believe that one is Pacific Took and Gauge, and the other is Holland Shooters Supply. Many hears back I had one from Holland, from a review that I had written, and I gave it to a friend who had a cratering problem with one of his 700 varmint rifles. He fitted it, and it solved his problem. Getting back to my Viper, it has been my experience that I can get away with a lighter firing pin spring with its tip diameter, with no accuracy issues. If you have an issue wiht a larger tip diameter the first two things that I would suggest you do is to check the weight of your spring, and take a look at the tip shape.

Thanks for the advise...

 

[boltfluter]

.062” seem to solve the problems so I can’t see any advantage to going smaller. It’s just not needed. And at some point your going to start poking holes of it gets too small .

This. Plus the poor bastard doing the job has to drill a nice, straight .048 size hole!! Drilling one at .059 is hard enough! And sharpening a .059 solid carbide drill is lots of fun for everyone. Lol.
Paul

 

[jepp2]

but, if your firing pin hole edges are nice and square you may solve a cratering problem without bushing the bolt face

Remington has been known to chamfer the edges of the FP hole on some rifles. I had the misfortune to own one. Here are the before and after pics.

 

[Texas Solo]

I was blanking primers badly. Having my bolt bushed solved all my problems.