Punctured primers

[LCazador]

[QUOTE="Uncle Ed, post: 37402552, member:
I appreciate the article , I would send pics. but have not figured that out yet. I have been working on this all morning and conclude that it was pressure/headspace and possibly the firing pin and hole . I pulled bullets and cut back the powder by 1.5 grains and all was fine, all but the pin is striking off center and still have a bit of mushrooming,like pin hole may be to big. Headspace as near as I can tell is around .004-.006. Micked some factory Lapua and it is about .007 shorter than may chamber.

I had the same issue with my 22BR even with light loads. Got the firing pin turned down and the hole bushed and it all went away. BTW Gretan replaces the firing pin spring also.

 

[savagedasher]

What was the ES with each ? And the Speed and were all target 4 shots

 

[Webster]

Loaded up some 6br with 30.5 grains of Varget in Lapua cases and 107 SMK's with 7.5 Remington primers and punctured most of them? The brass was full length sized ,headspace .003 off and trimmed .005 under. Shot some of the same loads with cci's with no problems. There was no pressure signs on case and bolt lift was fine

Maybe you have a tight barrel?

 

[muleman69]

Maybe you have a tight barrel?

Looking that way. Thanks

 

[Webster]

Looking that way. Thanks

Anyone know what typical tolerances are for land and groove?

 

[muleman69]

Anyone know what typical tolerances are for land and groove?

My other 6BR shoots this load lights out

 

[Flouncer]

Said herein by way more experienced loaders than I. Remington 7.5s are softer/not softer than other primers.

Which is it ? Fwiw what is the difference between Federal Magnum or regular large and small rifle primers ?

First time I have seen here in print "blanking" primers. What does that even mean ? Mushroomed, flattened, rounded radius, pierced, all self evident. - thanks !

 

[Dusty Stevens]

Said herein by way more experienced loaders than I. Remington 7.5s are softer/not softer than other primers.

Which is it ? Fwiw what is the difference between Federal Magnum or regular large and small rifle primers ?

First time I have seen here in print "blanking" primers. What does that even mean ? Mushroomed, flattened, rounded radius, pierced, all self evident. - thanks !

Blanking is the correct term but only a few will jump you for it. We know what you mean.

http://www.advantagefabricatedmetals.com/blanking-process.html

 

[Flouncer]

Thanks Dusty.

 

[Texas10]

A too sharp firing pin, excessively sized or short cartridge case (or other factors) will pierce a primer whereas excessive chamber pressure and/or too large a clearance between firing pin and bolt face and/or weak firing pin spring will blank a primer. The important difference is that the blanked out portion of the primer cup will be forced up the firing pin channel, causing all sorts of issues requiring disassembly of the bolt to clear the debris out before continuing to fire.

It is also an early warning sign of an impending over pressure event.

For in interesting perspective, try calculating the force acting against the primer cup with chamber pressure of 70,000 psi and a firing pin hole diameter of .072"

Apologies if that sounds a bit like hand loading 101 but since we have a certain number of silent lurkers who may be new to the sport, I thought I'd add a bit of detail.

 

[muleman69]

A too sharp firing pin, excessively sized or short cartridge case (or other factors) will pierce a primer whereas excessive chamber pressure and/or too large a clearance between firing pin and bolt face and/or weak firing pin spring will blank a primer. The important difference is that the blanked out portion of the primer cup will be forced up the firing pin channel, causing all sorts of issues requiring disassembly of the bolt to clear the debris out before continuing to fire.

It is also an early warning sign of an impending over pressure event.

For in interesting perspective, try calculating the force acting against the primer cup with chamber pressure of 70,000 psi and a firing pin hole diameter of .072"

Apologies if that sounds a bit like hand loading 101 but since we have a certain number of silent lurkers who may be new to the sport, I thought I'd add a bit of detail.

No problem, good info. Remove pin and looks good

 

[243winxb]

For in interesting perspective, try calculating the force acting against the primer cup with chamber pressure of 70,000 psi and a firing pin hole diameter of .072"

Page 13 at link in post #1 http://forum.accurateshooter.com/threads/primer-output-pushes-bullets-into-rifling.3966017/

The pressure in the primer pocket is calculated to be approximately 23,890 psi/V (165 MPa/V).

Primer only.

https://apps.dtic.mil/docs/citations/ADA599210

For this experiment the spit-hole diameter was reduced from the mil-spec 0.078 in to 0.055 in. As figure 4 illustrates, this reduction in area increased the force exerted on the primer cup by 20 times when compared to the no. 34 primer output

Through the course of the experiments the M80’s no. 34 primer produces very little initial force output. This is contrary to what has been previously observed with the no. 41 primer used in the M855 cartridge. However, when the spit-hole area is reduced the force witnessed in the primer pocket is about three times that of a no. 41 primer and 20 times that of a no. 34 primer with standard spit-hole areas. Similar results were observed in fully loaded cartridges.

The primer makes pressure , no powder needed.

 

[savagedasher]

I have a friend that was having that problem he cured it with the correct head space on the case
Expander ball was the problem

 

[243winxb]

A pocket depth of .123" and a primer of .126" will be above the case head by .003" when looking at SAAMI maximums.

Had some 38 special brass with shallow pockets. Using low pressure target loads, i would get a pierced primer sometimes. I smashed primers into the pockets with an RCBS Ram prime Unit so the were flush with the case head.

After uniforming the pocket depth, no more pierced primers. The primers were now .007" below the case head.

Pierced primers are not always a pressure problem.

 

[swd]

Sloppy firing pin holes are extremely common and the most common thing to cause blanking. Bush the hole and turn the pin down while your at it and there's a 95% chance the problem will be no more. And with the small pin you can take full advantage of all a Lapua case has to offer pressure wise, and then some..

 

[Texas10]

Page 13 at link in post #1 http://forum.accurateshooter.com/threads/primer-output-pushes-bullets-into-rifling.3966017/

Primer only.

https://apps.dtic.mil/docs/citations/ADA599210



The primer makes pressure , no powder needed.

Primers make a LOT of pressure. I remember one talented actor putting a revolver loaded with a cartridge with primer only to his head and insisting to his co-star he wouldn't be hurt. The force blew a plug of his skull into his brain killing him on the spot. Show got cancelled. Darwin award of the year, posthumously awarded of course.

Another demonstration occurred on my loading bench last year. Annealing a 6BR case with a FTF primer I neglected to pull first, I had just tossed the case into a pan with others after annealing with torch when the primer popped. Force of the primer blowing completely flattened an adjacent 6BR case. A real eye opener - after my ears stopped ringing. Interestingly, the primer stayed seated and didn't eject out the pocket.

 

[Webster]

Primers make a LOT of pressure. I remember one talented actor putting a revolver loaded with a cartridge with primer only to his head and insisting to his co-star he wouldn't be hurt. The force blew a plug of his skull into his brain killing him on the spot. Show got cancelled. Darwin award of the year, posthumously awarded of course.

Another demonstration occurred on my loading bench last year. Annealing a 6BR case with a FTF primer I neglected to pull first, I had just tossed the case into a pan with others after annealing with torch when the primer popped. Force of the primer blowing completely flattened an adjacent 6BR case. A real eye opener - after my ears stopped ringing. Interestingly, the primer stayed seated and didn't eject out the pocket.

When I was about 15 YO I took a pipe about 3.5" long with a 1/4" hole in it. I used a paper punch a cut out the powder charges from about 8 caps from a toy pistol that took rolls of the little powder charges. I made a small hole in the side to set it off. Put it in a vice in the garage and put a 3/4" board in front to catch the pellet. The pellet went threw the board and the garage wall. I was in Vietnam, you cannot believe how small the powder charge is to sent an 81mm. mortor round 3 miles.