Pierced primer help.

[amamnn]

Several custom barrels I own have the cartridge, twist and chamber (neck diameter) info etched on the chamber end face of the barrel. I have never had to look for it as I was installing the barrels and could verify that the info matched my specs when I ordered the barrel. Taking the rifle apart to look is a PITA, though..............

 

[bigedp51]

The firing pin hits the primer and pushes the case forward until it is stopped by the shoulder of the chamber and the cartridge goes bang. When the head clearance is excessive the primer is forced back over the firing pin and pushes the the firing pin dent out of the primer. It is the rearward movement of the case until it contacts the bolt face that causes the cookie cutter effect and punches the center out of the primer.

According to the link below the firing pin protrusion should be ,52 to .60, I would double check at SavageShooters.com for the the protrusion.

Savage Bolt Head Change Procedure
http://www.switchbarrel.com/BOLTHEAD.htm

 

[BoydAllen]

Factory loaded rimless ammo usually has generous clearances, and gets routinely fired that way without primers being pierced. On the other hand I would like to know what the the difference between loaded and fired cases, datum to head, is for the examples shown by the OP, measured with a proper tool. On the firing pin fall thing, Bob Greenleaf (who spent 25 years as an engineer for Savage Arms) has written that he sets his personal Savages to .035 protrusion so somewhere between the common figure of .055 and that you should be OK.

 

[bigedp51]

Factory loaded rimless ammo usually has generous clearances, and gets routinely fired that way without primers being pierced. On the other hand I would like to know what the the difference between loaded and fired cases, datum to head, is for the examples shown by the OP, measured with a proper tool. On the firing pin fall thing, Bob Greenleaf (who spent 25 years as an engineer for Savage Arms) has written that he sets his personal Savages to .035 protrusion so somewhere between the common figure of .055 and that you should be OK.

There is a very good reason why the military crimps their primers, also military ammunition is to have the primers .006 to .008 recessed below the surface of the case and they have much longer headspace settings. Meaning how many crimped primers fired in military chambers do you see with pierced primers?

You also have people uniforming their primer pockets and "increasing" the distance that the primer can move back over the firing pin. In over 46 years of reloading and hunting I have never seen factory loaded ammunition with a pierced primer, "BUT" I have seen plenty of reloaded ammunition with pierced primers.

The rifle in question was bought used and apparently rebarreled, so the firing pin protrusion and headspace should be questioned. If the resizing die is raised and backed off from the shell holder until the case is a snug fit and then lowered .002 this "might" fix the problem if the firing pin protrusion is correct.

And below is copied directly from the Sierra reloading manual, meaning if the firing pin has the proper tip radius and protrusion the biggest cause of pierced primers is head clearance.

The amount of head clearance and primer rearward movement to meet the bolt face is what punches the center out of the primer. (cookie cutter effect)

And if the original owner was a shade tree mechanic and amateur gunsmith the scotch tape he used on the back of his GO gauge might have been made in China and out of calibration when he set the headspace. :

And the pierced primer below was caused by the reloader following the die setup instructions with a AR15 rifle with longer headspace settings and causing excess head clearance.

 

[Patch700]

Here is a picture of the two cases. One had 29.5 Varget, the second had 30.3 Varget.

I am going to send bolt assy. to Greg Tannel. Also, trying to find someone with bore scope to check inside.

My measurement on the firing pin depth is about .062" and have heard that is very deep, put back to .045 or so and try that.
Does that make sense? Or now wait until Greg has reworked the bolt head, then set depth.

Thanks,
Kirk

As stated earlier your pin protrusion of +.060" is certainly not helping matters.... .050" would be a max and in all probability .040" would be ideal.

If you can't get fire in the hole with a pin depth of .040" then there may be other factors such as a weak spring , incorrect installed height or the pin is hanging up in the bolt head.

Too much pin protrusion will give false readings with regards to reading primers , for example you may have a load that is in fact not approaching peak pressure but is showing signs of catering. . That same pin protrusion with a load that IS at peak pressure may actually pierce the primer where normally it would've simply shown small signs of cratering ..

Good luck.

 

[Old Navy]

I kicked this same dead horse around for over a year after first seeing a crater with normal pressure loads. The crater edge progressive got worst. Finally got a couple that would not slide in the shell holder. I tried cleaning and a new spring first. That did absolutely nothing. Greg bushed it and I have never looked back. The attached photo isn't very good but you can see what a .013" tall crater looks like. Later! Frank

 

[dkhunt14]

I have 62 thousandths pin protrusion on all my BAT actions and never pierced a primer. I use BR4 on my Dashers because they are the toughest. Matt