large or small firing pin

M

marion packett

Guest
I intend on shooting the 6.5 x 284 which uses large rifle primers and the 6.5 x 47L which uses the small rifle primers form the F class Panda action on a switch barrel rifle. Which size firing pin will be best for both cartridges, large or small?
 
The single reason for the smaller pin is so you can run hotter..... higher pressure.

So of course I'm all about small firing pins.

al
 
There is no doubt the smaller diameter firing pin will take the primer cup to higher pressure than the larger size. Kelblys offer their benchrest actions in 3 different diameters so which size you select makes no difference to them, but, Greg Walley ran some very extensive test using some elaborate electronic gizmo's. (Greg, while being a world class benchrest gunsmith at Kelblys is also very competent electronics wizard) Using an electronic setup to capture hang time, etc., he determined the larger, old standard diameter, gives the most consistent ignition.
 
thanks Jerry, that's the answer I'm looking for. Marion
 
I debated about rebushing my 40X bolt & firing pin for the smaller size, but since I'm shooting a 6BR in F-Class with it I find no fault in the standard pin size as I'm not interested in driving pressures to the roof.
Thanks for that info Jerry. Best to stay with more consistent ignition for the long range game.
 
Was there more hang fires with the small pin or was it a matter of inconsistent pressure which would make for scatterings rather than groupings
 
I don't know about large primers, but my Viper, that has a small pin tip, gives no indications of ignition problems that I can detect. I think that the crater thing can have a lot to do with other factors as well, like pin to hole fit, tip shape, pin weight, and spring weight. Once, along time ago, I made a stupid mistake and opened up a primer pocket on a double heat treat '03 that had a later model bolt, and a very heavy aftermarket spring. The hole was a good fit, had very square edges, and although the primer fell out when I opened the bolt, it had no crater. I have been told that the proper shape for a standard Remington pin tip has a double radius. a larger one at the center, and a smaller one at the edge. If the radius extends too far back from the tip, and the pin is light enough and the spring light enough, pressure backs the pin up to the point where the radius is below the edge of the hole creating space for a crater to form. Too much side clearance makes it worse.
 
Marion,
Listen to Boyd. My Bats and Stiller receivers have small pins and I had my Remington bolt bushed and used a small pin. Jerry Stiller had a great scientific article on firing pin sizes in Precision Shooting. Not empirical data, just facts.
 
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