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  #31  
Old 09-14-2014, 06:33 PM
trotterlg trotterlg is offline
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Bushing the bolt face to a smaller and tighter pin fit would be best, however, the main problem is the space between the pin and hole. Primer material flows into the gap and can cut or "blank" the primer. It is an order of magnitude easier to put in a slightly oversized pin than it is to bush the bolt face, plus, it is likely something that you can do on your kitchen table. Larry
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  #32  
Old 09-14-2014, 07:01 PM
snowpro440 snowpro440 is offline
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http://www.jamescalhoon.com/primers_and_pressure.php
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  #33  
Old 09-14-2014, 09:12 PM
Chad Chad is offline
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I would gladly pay someone to bush my bolt on the CZ, BUT I haven't been able to find anyone that has time right now or can do the work on these hardened bolt faces. I'm all ears if you know someone that does!

Yesterday, I made the tip of the firing pin just ever so slightly more blunt (thanks SDguy605 for the guidance!). I chucked the pin in the drill and used a piece of extra fine sandpaper over a piece of heavy glass. Took about .002" off. Then I polished the tip with my dremel tool afterwards. I also swapped out the spring with a stiffer striker spring from JnP springs.

Took it out and shot it today and while there is still some slight cratering, it is MUCH better. I got my powder charge back up where I want it and am no longer worried about it blanking primers.

I shot a quick 5 shot group that measured right at 3/4" at 200 yards, pretty good considering there was a wacko at the next bench shooting a 1903 30-06 while STANDING ON TOP of the bench. That dude made me nervous! I immediately left after firing the 5th shot. Gotta love the public rifle range.

I will still be looking for someone to bush the bolt, but in the meantime I will go forth and kill coyotes with the 17-204.

I believe Adam is still trying to get ahold of Kiff about the oversized CZ firing pins. I'm hoping it happens! I would like to try one (or two) for myself.

Last edited by Chad; 09-14-2014 at 09:27 PM.
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  #34  
Old 09-15-2014, 01:25 AM
Kevin Gullette Kevin Gullette is offline
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Red face Ok......one more time.

Cratering occurs when the firing pin is forced, by pressure, slightly to the rear.....exposing the boltface hole bore by the pin's hemispherical tip, creating a gap. This gap is then filled by primer cup metal.....making a primer crater. Too much movement, of the firing pin tip, rearward.....and the primer blanks.

As a reference, and a good read, refer to Precision Shooting magazine, May 2001, page 31, "The Real Reason Primers Pierce" by Jerry Stiller.

Chad: A stronger firing pin spring does help a bit.....doesn't it?!

Hope this helps.

Kevin
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  #35  
Old 09-15-2014, 10:29 AM
Kevin Gullette Kevin Gullette is offline
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Lightbulb Also.........

We've been through this before.

Search "Bushed firing pin", back in May 2012, on this site.

Interesting discussions.........

Kevin
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