Pierced primer help.

[4xforfun]

A friend of a friend called me and says he is piercing primers. He just baught a used Savage 6br and is up to 29 g Varget with 105 VLD'ds and CCI 450's. He is not sure if it is the factory tube, as there is no markings anywhere on the tube. I have never had the problem, and actually, have never loaded for the straight 6br, although my FF loads for my Dasher is 31 G varget/105/450 combo, so I don't think it is a hot load. it is my understanding that one of the fixes for this is to switch to the 450 primers!! We are already there.

Anyone??
Thanks,
Tod

 

[bigedp51]

Below is from the Sierra manual

Bumping the shoulder back too far causes excessive head clearance, this can cause the firing pin to punch the center out of the primer just like a cookie cutter.

Below an animated image of a cartridge being fired and primer movment.

Excess head clearance on AR15 and the anvil pluging the hole in the primer.

 

[dkhunt14]

Big Ed is right if you bump the shoulder back too much it will pierce primers. The only Br4 primers I ever saw blanked in Dasher and a Bat action is where the shooter was bumping them 5 thousandths. The BR4 primers are the toughest primer. When the guys at Williamsport use 450 primers they eventually pierce them. You can't compare what you fireform with and what is shot in a Br. When you fireform you lose a lot of energy blowing the brass forward. Different barrels and different throating can really change the load from one to another. It could also be the pin or the bolt needs bushed. Matt

 

[Drop Port]

As stated headspace and non bushed / custom fit small diameter pin of a combination of the two or three. Also check a fired case and measure the fired neck dimension. If factory brass is fired in a tight neck pressure will come on early exaggerating all or some of the possible culprits.

 

[NorCalMikie]

Headspace (brass not fireformed to the chamber) would be my first guess. Don't blame the firing pin or rifle till you get formed to chamber cases. Got a "few" Savage rigs with "no bushed" firing pins and never had a problem.

 

[243winxb]

29 g Varget with 105 VLD'ds

6br http://www.6mmbr.com/6brfaq.html#23415 Maybe find out what chamber is in the barrel?

 

[Erik Cortina]

If no markings on barrel it suggests an aftermarket barrel is installed. It is possible that headspace was not set properly by installer. Check headspace with gauges before proceeding.

 

[Ggmac]

You mite also check firing pin spring ,Or a replaced firing pin with a small ,when it was a large ( savage ha 2 diff firing pin diam ) or wrong bolt head , again it must match the size of the firing pin .

 

[bigedp51]

4xforfun

Military firearms and especially older milsurp rifles have long and longer headspace settings than commercial firearms. Some of the milsurp rifles I have owned had .017 head clearance and never piercing a primer.

It is my belief that chamber pressure and the thickness of the primer cup has more to do with this than anything else. Meaning the case should be a closer to matching chamber headspace length before increasing the load.

Tell your friend to chamber a empty resized case that has a primer started into the primer pocket just using finger pressure letting the bolt seat the primer. The amount the primer is protruding is your head clearance which should be only .001 to .002. (cheap bastards headspace gauge)

Measure the over all length of the case "before" inserting the primer and again after the bolt seats the primer, the difference between the two is your head clearance. Also note the force of the firing pin hitting the primer can make the case even shorter depending on annealing and the softness of the brass.

 

[4xforfun]

As stated headspace and non bushed / custom fit small diameter pin of a combination of the two or three. Also check a fired case and measure the fired neck dimension. If factory brass is fired in a tight neck pressure will come on early exaggerating all or some of the possible culprits.

Pretty sure that his is a no turn neck by what he told me. He said that his loaded rounds are .266 and his fired casses are .268 - 269. I would think that there would be some springback on the brass, so my guess is that it is a .270 - .271 chamber. This is, of course, conjecture on my part.

 

[rock1455]

I am the friend with the problem. Thanks for 4xforfun for presenting my problem.
I am new to this with a used Savage 6mmBR F-Class used rifle with what I believe has had the barrel replaced, but previous owner deceased so cannot get history. It says 6mm BR Norma 272 NK on inside of chamber area with some other writing on opposite side that is out of my sight possibility.
Anyway,

I am using new Lapua cases. Unfired. I shot about 80 the day before without a problem, just some cratering on loads with about 29.5 + of Varget.
Yesterday, the thirdload of 105 Amax, 30.3 Varget seated on lands and 5th round(105 AMAX 29.5 Varget seated .010 into lands) got the primer hole and the small metal from primer was forced into firing pin hole in bolt that I removed and continued on until it happened second time, then I quit.

It was an 80 degree day and cases were sitting on bench.

I have checked the headspace method noted above between new and once fired cases and found about 0.003 difference in case oal from head to primer seated with bolt method.

The primers extrude from bolt seating about .006 inch and the bolt face looks worn and slightly rounded at firing pin hole.

The firing pin extrudes about .060 as best as I can measure.

I thought I would try a new bolt face, but also need to get headspace go-no gages it looks like before I try that.

Any better suggestions?

 

[bigedp51]

Raise your resizing die and use a .006 feeler gauge between the shell holder and the bottom of the die and resize a fired case and check your head clearance and see if it decreases.

 

[243winxb]

the thirdload of 105 Amax, 30.3 Varget seated on lands and 5th round(105 AMAX 29.5 Varget seated .010 into lands ) got the primer hole and the small metal from primer was forced into firing pin hole in bolt

Reduce the powder charge?

 

[jo191145]

Someone correct me if I'm wrong but isn't .272 neck the new measurement used for Lapua brass after they thinned the necks in manufacturing? Prior to that a slight neck turning was required?
It's been a lot of years since I loaded for a 6 BR and my memory no longer retains information as it once did.

You may be using older brass in a newer dimensioned chamber. You may have new brass with a larger neck wall thickness similar to old. You may have some thicker bullets from Hornady. With the high demand for components we must expect quality control to decrease.

Between a possible tight neck and exposure to the sun you may have the answer.
That being said I had a shilen 8 twist tube that could not be shot using the competition loads listed on these pages.

 

[LRPV]

"Blue box" no turn neck is considered to be .2704".
.272" was no turn for "gold box".

 

[BoydAllen]

Could you post a reasonably sharp picture showing the head of one of the cases that has a pierced primer? I would be looking at the corners of the primer for pressure signs. If the corners look normal, then you do not have a pressure problem, and we can look elsewhere. If the corners of the primers are very sharp, then you have pressure, and you may have other issues as well. For the bolt, the usual good advice is to sent it, including the striker assembly, to Greg Tannel at Gre Tan Rifles, to be bushed and have the hole and pin diameter reduced to a nominal .062. His price is very fair, work excellent, and turnaround fast. His reputation is excellent. Another thing that can happen, that can be hard to see without a bore scope, is that hard carbon that resists normal cleaning methods, can build up in chamber throats. While this may not be the issue at all, if someone you know has a bore scope, a quick look, after you have cleaned the barrel normally, is always a good idea. Getting back to the pressure issue for a moment, when you reprimed the cases that had pierced primers, did the pockets feel loose? If a rifle that does not have mechanical issues, pierces primers, with ammunition that fits its chamber properly, the pressure would usually be high enough to expand primer pockets to some degree.

 

[rock1455]

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

 

[BoydAllen]

The idea that excessive firing pin protrusion could be responsible for blanked or pierced primers is based on a false premise, that the firing pin's forward motion (when actually firing) is stopped by the shoulder on the firing pin. It is not. It is stopped by the primer, and never gets to full extension. The corners of your primers are well rounded. Have you taken your bolt apart and looked for primer pieces that may be causing problems? Also, have you examined the tip of the firing pin for gas cutting cause when primers were pierced or blanked? This can cause subsequent primers' cups to be cut in a way that weakens them, and leads to more piercings.

 

[jo191145]

"Blue box" no turn neck is considered to be .2704".
.272" was no turn for "gold box".

Thank You for the correction and trip down memory lane

 

[4xforfun]

Looking at the pictures...I agree with Boyd. BUT...it looks like the 30.3 primer is considerably flatter than the 29.5. IMO, you are getting close to max PSI. Sorry I couldn't be more help on the piercing issue.

Tod