Of center primer strikes and fliers

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mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Of center primer strikes and fliers

Post by mdeland »

I read a while ago that some bench rest folks believe this is true and wonder if it has application in mid and long range shooting.
The thinking, if i understand correctly, is that a center strike makes the primer anvil work more effectively/efficiently and translates to more consistent flash pressure and thus ignition.
Actually i have a notion what is really happening is off center strikes translates to the speed of ignition rather than pressure difference. My thought is that perhaps off center strikes make the timing of the primer ignition sporadic. Were talking mill-seconds of difference but possibly a factor in accuracy potential.
rgchristensen
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Joined: Sat Jan 16, 2016 10:51 pm

Re: Of center primer strikes and fliers

Post by rgchristensen »

Some years ago, the late Charlie Dell did some research on primer brisance. He used different strengths of primer-strike, rather than off-center strikes. Far as I remember, as long as the primer popped, he found no variation significantly greater than the usual primer-to-primer variation. Not an easy experiment to design, tho....... And he dug up some British military research from 1930's that seemed to indicate the same thing.

CHRIS
semtav
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Joined: Wed Feb 03, 2010 3:21 pm
Location: Montana

Re: Of center primer strikes and fliers

Post by semtav »

If that were the case, why would a light strike or broken firing pin cause accuracy problems ??

difference in lock timing causing shooter errors is the only other explanation I can think of
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desert deuce
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Joined: Mon Apr 14, 2008 10:51 pm
Location: Rio Rico, Arizona

Re: Of center primer strikes and fliers

Post by desert deuce »

Was shooting next to Hugh Wilson from 1,000 yards at Byers. (Using most accurate rifle I have ever encountered.) I shot three X's in a row. Next five shots all over the place. Had broken the tip off the firing pin. Replaced the firing pin, rifle groups back in center of target.

Acquired a beautiful completely reworked #3 Hepburn. Could not get the rifle to group. Bushed the block and increased firing pin protrusion, better, still not satisfied with accuracy. Installed new hammer spring from DZ Arms and then it became my go to long range rifle.

My reworked Ballard Pacific just not cutting it. Bushed front of breech block, installed new firing pin, still not satisfied. Installed new hammer spring and won the Raton five at 200 Match with it. Still shoots lights out.

Recently a Shiloh Sharps........insane vertical not typical of such rifle. Hammer fall hammer spring obviously not the problem. You guessed it, once the firing pin problem corrected the rifle has since won several championship level matches.

So, all I am able to discern from these experiences is that solving the ignition problems on these four rifles apparently corrected the inaccuracy problems and four out of four equals a pretty high success rate. :wink:
Sometimes you get the chicken, and sometimes you get the feathers!
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: Of center primer strikes and fliers

Post by mdeland »

Speaking of firing pin protrusion I set Large rifle at .064 +/- .002 . I got this from a Book written by a 50's gunsmith with the name of Roy Dunlap, a gunsmith who's advice I have yet to find wanting. He goes on to say small rifle should be set at .050 +/- .001 and .22 Rimfire at .037 +/- .002.
Shot gun should be in the .075-.085 range.
Protrusion needs to be checked after a few hundred rounds in new or rebuilt rifles in my opinion as firing pins will tend to get a bit deeper as the pin head mates into it's nest in the breech block or bolt face.
I find off center strikes quite common in falling block actions. They are especially common in HIgh and Low Wall Winchester actions and require link adjustment on the vertical. If off horizontally then the action barrel hole is generally off center and this fix requires a firing pin bushing in the breech block face and a new pin hole location.
I believe the bench rest guys are probably onto something with the center primer strike thing.
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