Why am i blowing primers ( Rem 7 1/2 br) ONLY

[Adam 6mm build]

 

[Adam 6mm build]

Oveus this was one that didn't pop anyway look at the primer strick

 

[carlsbad]

afret,
the pin doesn't pierce the primers. the pressure inside pushes the brass into the hole in the bolt and the firing pin force is actually small compared to the pressure inside. the brass has enough strength to span a small hole but not a big hole. --Jerry

 

[243winxb]

Where that come from? High pressure? Or from bushed bolt face?

 

[carlsbad]

The primer doesn't look like the cartridge has high pressure at all. See the rounded corners? Usually those flatten before you start getting piercing or even cratering. I am suprised this cartridge is piercing primers.

Those scratches don't look like they are caused in the rifle since the bolt only rotates about 90 degrees. Nore likely from brass prep.

--Jerry

 

[shoot4fun]

View attachment 1242709

Although "reading primers" can be deceiving I would say it is unlikely you are over pressure there.
This doesn't appear to be a sample of the issue you started this thread about either.
At this point I would like a clarification on just what you mean by blowing primers. To me, at least, blowing a primer means pressure is so great that it is pushing the primer completely out of the pocket. This is sometimes confused with piercing or blanking a primer which, again to me is when the firing pin punches a hole in the primer.

 

[6MMsteve]

Where that come from? High pressure? Or from bushed bolt face? View attachment 1242721

that looks very suspect to me...nothing in this picture is uniform at all

 

[NorCalMikie]

You'll get a "pierced" (blanked ?) primer when the head space is off. (brass shorter than the chamber from sizing or hasn't fire formed yet) Round fires, primer tries/can back out of the pocket from excess space, gets slammed back on the bolt face and firing pin punches a hole in it and it gets pushed back into it's pocket. Once the brass is fire formed, the pierced issue goes away.
Blanked primer refers to a gas blown primer?? Never seen that with my own eyes.

 

[Adam 6mm build]

I should have stated peirceing primers a complete hole through the primer several times I had to remove firepin and remove the little piece of brass from inside the bolt

 

[carlsbad]

Adam,
Since you know how to take your firing pin out and clean it, do you have a micrometer or caliper to get an accurate measurement of the diameter of the firing pin?

 

[Aero]

Hard to tell from the pic and maybe it's some sort of optical illusion, but the fp indent looks conical shaped and square at the bottom instead of nicely rounded from a hemisherical tip, kinda like you see with AK's and SKS's

 

[rogn]

From the evidence you are presenting it would appear that you have a variable that's entering the equation. Its something like an occasional defective primer cup, an occasional overload, an occasional out of pec bullet, a case that is binding in the neck(too long, too fat), or even a given round that's cooking in a hot chamber.
Results are too random to test by firing in another gun, cartridge.
Overall it sounds most likely Remi has a sample of bad primer cups. Bushing may well stop the problem, but if cups are issue it may not.

 

[Webster]

I'm having issues with blowing Rem 7 1/2 br primers please give some advice to correct the issue thanks Adam

29.4 gr of Varget is max load in my Berger load manual. Your shooting 29.0. May be to much in your rifle? Back off .3-.6 gr and see if the problem goes away. I have several Rem 700 and I can see a raised area around the indent get more pronounced as I increase the load. You don't have raised area, proably because your bushed. My rifles are not bushed. The first thing you should do when you have a primer problem is to back off the load and see if it goes away. Don't keep shooting a load that may be to stiff. I see no hint of primer flattening. Looks like a deep FP indent?

 

[foxguy]

Just guessing but the picture you have posted, the primer hit looks like it may be fairly deep?
Firing Pin protrusion? What should the Firing pin Protrusion be? De-cocked Bolt.

 

[NorCalMikie]

View attachment 1242709

Could that ring be from the firing pin "bushing" imprinting on the case head that got slammed back on the bolt face from too much head space?

 

[carlsbad]

Could that ring be from the firing pin "bushing" imprinting on the case head that got slammed back on the bolt face from too much head space?

better not be. Hope the firing pin bushing is not at a different plane than the boltface...that would not be good. but that's not what it looks like.

 

[Link]

picture of bolt face, can you see light through the primer ?

 

[243winxb]

https://discover.dtic.mil/

If the rounds head clearance allows the primer to back out .010" on firing, how does that equal a pierced primer?
The primer is stopped by the bolt face. With the primer against the bolt face and a set firing pin protrusion, the pin indent should be the same depth as zero head clearance?

If the primer backed out more on firing , there should be signs of gas leakage.
Does a bolt action firing pin remain in contact with the primer at firing? I think yes. So, to much pin protrusion will pierce primers?

High pressure may allow the primer cup to flow into the firing pin hole. The movement of metal has to come from some where. Metal flows up around the firing pin tip, thinning the cup. Pierced primer is from stretching of the cup metal.

 

[divingin]

I should have stated peirceing primers a complete hole through the primer several times I had to remove firepin and remove the little piece of brass from inside the bolt

Sounds to me like you are still getting cratering then. Or your FP tip profile is off.

You'll get a hole in the primer either from the primer being forced back against the extended firing pin to the point the pin is forced through (which should tear a hole) or from the primer flowing into the firing pin hole enough that the cup thins to its breaking point around the circumference of the flow (which will cause a slightly larger hole, and possibly leave the removed material inside the bolt.) If your firing pin tip profile has changed from radiused to squared off, that may act as a die and punch out a disk as well.

I've run over 29gn of Varget under a 105; I would't call it anywhere near a max load. I use CCI 400's as a general rule.

 

[Uncle Ed]

If the rounds head clearance allows the primer to back out .010" on firing, how does that equal a pierced primer?
The primer is stopped by the bolt face. With the primer against the bolt face and a set firing pin protrusion, the pin indent should be the same depth as zero head clearance?

If the primer backed out more on firing , there should be signs of gas leakage.
Does a bolt action firing pin remain in contact with the primer at firing? I think yes. So, to much pin protrusion will pierce primers?

High pressure may allow the primer cup to flow into the firing pin hole. The movement of metal has to come from some where. Metal flows up around the firing pin tip, thinning the cup. Pierced primer is from stretching of the cup metal.

The firing pin hits the primer and the excessive head clearance allows the primer to move back over the firing pin and it acts like a cookie cutter and punches the center out of the primer. This is why military primers are crimped, it keeps the primer from moving to the rear.