.075 vs .0625 firing pins and small primers?
- Thread starter Lucky6547
- Start date
Ken,
Get the firing pin turned down and the bolt face bushed . I did it on my Remington for the 6BR and 6.5x47 cartridges. Made a big difference in how much further I could work the powder charge up because the primer was no longer getting pierced. GRE-TAN rifles does a great job with a very quick turn around on this operation.
dmoran
Donovan Moran
Cratering .... that will be excessive early in the charge/pressure/velocity ladder.
For me, its a must to go .0625", ether by going to a small pin bolt or bushing the .075" bolt.
GRE-TAN Rifles does excellant bushing work in fast turn-around time.
Good Luck
Donovan
BoydAllen
Gold $$ Contributor
If the larger pin has a properly shaped tip (smaller radius at the edges lager in the center, not a hemisphere), fits the hole well, and the hole has a sharp edge, it will not be a problem. The problem is that this is hardly ever the case for factory actions. Greg Tannel's work is excellent, affordable, his turnaround is quick, and I do not know of any disadvantage associated with the smaller tip diameter. For factory rifles, If I am not having an issue with pierced or blanked primers, I shoot them as is, and live with the cratering. My custom actions have the smaller pin tips, and I am glad of that, because I think that they have good ignition, and seem to be more tolerant of differences in pin and spring weights.
Once I had a double heat treat '03 Springfield that I accidentally overloaded to the point where the primer fell out when I opened the bolt. (a loooog time ago, and only once) Those actions have very heavy firing pin assemblies, heavier than any commercial action, and mine had been fitted with a the heaviest spring that strong hands could assemble. The bolt was a well made new '03A3 Remington, that had been made to the highest standard, of fit, the hole was very square, and fit the pin tip very well. When I examined the primer that had fallen out of the case, there was absolutely no crater. Think about that for a bit. Neither was it blanked or pierced. I would not choose to have a pin that was that heavy in any of my modern rifles, or a spring that was that heavy, but with those, and a firing pin tip that was the same diameter as the larger of the two you inquired about, that was the result.
Once I had a double heat treat '03 Springfield that I accidentally overloaded to the point where the primer fell out when I opened the bolt. (a loooog time ago, and only once) Those actions have very heavy firing pin assemblies, heavier than any commercial action, and mine had been fitted with a the heaviest spring that strong hands could assemble. The bolt was a well made new '03A3 Remington, that had been made to the highest standard, of fit, the hole was very square, and fit the pin tip very well. When I examined the primer that had fallen out of the case, there was absolutely no crater. Think about that for a bit. Neither was it blanked or pierced. I would not choose to have a pin that was that heavy in any of my modern rifles, or a spring that was that heavy, but with those, and a firing pin tip that was the same diameter as the larger of the two you inquired about, that was the result.
Got mine back from Greg today looks fantastic only took him a month not the 6-8 weeks he claimed so I'm really happy. 
Lucky6547
Silver $$ Contributor
Thanks for the info guys...so if you were planning to stay with the larger firing pin...would you go with a different caliber? Do you think an older 40x would have an issue with the smaller primers?
I could go 6mmSLR on this build as well instead of a 6mmBR...the club I shoot at seems to have a fairly even split of shooters using both calibers...600 yard informal competition...
I could go 6mmSLR on this build as well instead of a 6mmBR...the club I shoot at seems to have a fairly even split of shooters using both calibers...600 yard informal competition...
Moving to a Large Rifle primer cartridge does reduce the problem dramatically. I had an FN SPR A4/A2 rebarrelled from 308 to 6.5X47 Lapua some years back and it was nearly useless. Viht's not exactly 'hot' loads produced severe cratering at starting loads and blanked BR primers at starting loads plus a couple of grains.
A simple rechambering to 260 Rem solved the problem and the rifle would now produce a shade under 3,000 fps from 123gn Scenars (30-inch barrel) with only mild cratering. Precision is excellent too and I don't think I've lost much by the chambering change.
Alex Wheeler
Site $$ Sponsor
I bush firing pins down to .062 and turn the pin to fit. You will be able to run higher pressures before cratering a primer. There is also the added benefit of firing pin guidance when bushed properly. You get rid of the funnel Remington has in there and guide the pin straight the whole way.
DHD
Silver $$ Contributor
They have answered your question very well. The only thing I can add is that there is no downside to having a small firing pin regardless of whether you use a small primer or large primer. Other than the $ of having the work done that is.
I had Gre-Tan bush 5 of mine and 2 were for large primer cases.
Not to take anything away from Mr Tannel, but there are now others that advertise doing this work.
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