Bushing firing pin?
- Thread starter Mram10
- Start date
John Kielly
Shari's fan club
I would have thought that a custom benchrest action would be adequately machined & not require remedial work.
Pete Wass
Well-known member
GeneT
Active member
Thank you. I was considering a sleeve and use the oem firing pin. Your way sounds easier
I watched that before, thanks. Was looking for a tutorial. I found one write up without pictures.
vtmarmot
P Magoon, Livin' Free NH
I have a Savage Long Range Benchrest in 6MM BR. It was cratering and giving off-center primer hits. Also, the accuracy had fallen off a good bit from its early years.
I sent the bolt to Greg and it came back quickly. No more cratering and no more off-center primer strikes.
Now, you can't send someone a bolt and expect the entire rifle to suddenly shoot a lot better. I have not spent the time to find the load, seating depth etc. that it wants now. However, I'm a step further along the road. I am happy with his services.
I sent the bolt to Greg and it came back quickly. No more cratering and no more off-center primer strikes.
Now, you can't send someone a bolt and expect the entire rifle to suddenly shoot a lot better. I have not spent the time to find the load, seating depth etc. that it wants now. However, I'm a step further along the road. I am happy with his services.
They bend & break when turned straight.
There is/was a reason the firing pin had a taper from the stop shoulder to the tip.
Mram10,
Thank you. I was considering a sleeve and use the oem firing pin. Your way sounds easier.
Order a D.Holland oversize pin & ream the breech face for a few thousandths clearance....done.
Practice bushing the breech face,after you have seen a tutorial w/ pictures.
WSnyder,
I've never had to replace the firing pin on a J.Borden bushed bolt or firing pin.
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Thanks. Will do
Thank you. I’ll check it out
Kevin Gullette
New member
Years ago........
......I posted the following on the saubier(small caliber)board.
As a reference, and a good read, refer to Precision Shooting magazine, May 2001, page 31, "The Real Reason Primers Pierce" by Jerry Stiller.......you know....the guy who designs actions.
Hope this helps.
Kevin
......I posted the following on the saubier(small caliber)board.
As a reference, and a good read, refer to Precision Shooting magazine, May 2001, page 31, "The Real Reason Primers Pierce" by Jerry Stiller.......you know....the guy who designs actions.
Hope this helps.
Kevin
Thanks. No idea where I’d find that issue but I’ll google it
Butch Lambert
Active member
Kevin, that article is great and has the engineering data to back up the small firing pin. Of course Dan is right. It is all futile if your firing pin is a sloppy fit.
Kevin Gullette
New member
Butch,
As far as blanking is concerned.....the article points to only the boltface hole diameter, as the primary culprit. I do agree that a good f.p./hole fit is good practice.....but unrelated to blanking.
This make any sense??
Anyway......my 2 cents.
Kevin
As far as blanking is concerned.....the article points to only the boltface hole diameter, as the primary culprit. I do agree that a good f.p./hole fit is good practice.....but unrelated to blanking.
This make any sense??
Anyway......my 2 cents.
Kevin
Butch Lambert
Active member
I'm a little confused. I'm of the impression that a .062 firing pin in a fitted hole will prevent blanking. Excess headspace and a weak firing pin spring can contribute to this.
Kevin Gullette
New member
Butch........
Here's some more of my old posting on the small caliber board.
A little Jerry Stiller math.....
A 0.082" firing pin probably has an 0.084" boltface hole. The hole is 0.005412 square inches. At 50,000psi, this results in a total shearing force of 277.1 pounds.
Now use a 0.060" firing pin, with a 0.062" boltface hole. The hole is 0.003019 square inches. At 50,000psi, this gives a total shearing force of 151.0 pounds.
So.....for a 0.022" reduction in the boltface hole diameter, there is a 45.5 percent reduction in the shearing force.
As would be expected, a stronger firing pin spring has little effect.........been there, tried that.
Why these things only seem to happen with small rifle primers AND small calibers????.....I do not know, or can prove........but I strongly suspect that as the sectional density is lowered, a more "focused" pressure spike through the flash hole is created.....and the firing pin is pushed rearward. BUT.......that's just me.
BTW.....my old 20BR had about the same situation as above. Quite an eye-opening experience. Greg Tannel reduced the firing pin diameter, and bushed the boltface to a smaller firing pin hole size. The result.........with 40gr bullets blanking at 3400fps.........to NO cratering whatsoever at 4150fps.
Hope this helps.
Kevin
Here's some more of my old posting on the small caliber board.
A little Jerry Stiller math.....
A 0.082" firing pin probably has an 0.084" boltface hole. The hole is 0.005412 square inches. At 50,000psi, this results in a total shearing force of 277.1 pounds.
Now use a 0.060" firing pin, with a 0.062" boltface hole. The hole is 0.003019 square inches. At 50,000psi, this gives a total shearing force of 151.0 pounds.
So.....for a 0.022" reduction in the boltface hole diameter, there is a 45.5 percent reduction in the shearing force.
As would be expected, a stronger firing pin spring has little effect.........been there, tried that.
Why these things only seem to happen with small rifle primers AND small calibers????.....I do not know, or can prove........but I strongly suspect that as the sectional density is lowered, a more "focused" pressure spike through the flash hole is created.....and the firing pin is pushed rearward. BUT.......that's just me.
BTW.....my old 20BR had about the same situation as above. Quite an eye-opening experience. Greg Tannel reduced the firing pin diameter, and bushed the boltface to a smaller firing pin hole size. The result.........with 40gr bullets blanking at 3400fps.........to NO cratering whatsoever at 4150fps.
Hope this helps.
Kevin