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Help reading a primer, overpressure?
- Thread starter Glockadopoulos
- Start date
looks like brass from a blowback action gun.
Weak firing pin spring....
I am in line with GreyBeard's answer:
excess headspace allowed the brass to move forward with firing pin strike, as the charge ignited the brass case expanded and gripped the chamber walls, preventing it from pushing firmly against the breech face, the primer then began to blow out but did not because it is in fact a relatively light load.
You can reload it.
excess headspace allowed the brass to move forward with firing pin strike, as the charge ignited the brass case expanded and gripped the chamber walls, preventing it from pushing firmly against the breech face, the primer then began to blow out but did not because it is in fact a relatively light load.
You can reload it.
It's over pressure.
The issue is why?
The most common factor I have found is a fast powder and a heavier bullet but as described above other factors may come into play.
Also folks attempting to hot rod 9mm to increase power factor come across this issue. The brass can be reloaded but it's lifespan is compromised and shortened. If significantly bulged near the bass or the case mouth seems excessively thin then toss it.
I use a Lee 9mm bulge buster (special order .380 Mak modified die) to reduced minor swelling near the base and resize to near factory, in order to use in all chambers of several pistols.
The issue is why?
The most common factor I have found is a fast powder and a heavier bullet but as described above other factors may come into play.
Also folks attempting to hot rod 9mm to increase power factor come across this issue. The brass can be reloaded but it's lifespan is compromised and shortened. If significantly bulged near the bass or the case mouth seems excessively thin then toss it.
I use a Lee 9mm bulge buster (special order .380 Mak modified die) to reduced minor swelling near the base and resize to near factory, in order to use in all chambers of several pistols.
http://www.redding-reloading.com/tech-line-a-tips-faqs/145-dealing-with-headspace
Barrowed from Redding Reloading article:
Headspace is like Goldilocks porridge. It has to be just right for the best accuracy. Too much is bad and too little is also bad. So how do we know when we have too much headspace? There are a couple of obvious tell tale signs on our fired cases that are sure fire indicators. The first is a protruding primer. If, after firing, you see the primer is backed out of the primer pocket, even a little bit, you have excessive headspace. Remember, the top of the primer in an unfired case is supposed to be located just below the case head after it has been seated. If it's sticking out after the shot has been fired, the case is too loose in the chamber.
The second indication of too much headspace is a excessively stretched case. When the powder is ignited, the case is expanding in all directions, including front and rear. Brass does have a limited amount of "springback", but when the amount of headspace exceeds the ability of the case to springback, the case will be permanently stretched and weakened. Stretched cases can be easily identified by a bright, light colored ring located just forward of the head. The case at that point has been stretched dangerously thin. Those cases should be thrown away immediately as they will come apart at that point sooner or later. Case head separations can sometimes be very nasty.
Barrowed from Redding Reloading article:
Headspace is like Goldilocks porridge. It has to be just right for the best accuracy. Too much is bad and too little is also bad. So how do we know when we have too much headspace? There are a couple of obvious tell tale signs on our fired cases that are sure fire indicators. The first is a protruding primer. If, after firing, you see the primer is backed out of the primer pocket, even a little bit, you have excessive headspace. Remember, the top of the primer in an unfired case is supposed to be located just below the case head after it has been seated. If it's sticking out after the shot has been fired, the case is too loose in the chamber.
The second indication of too much headspace is a excessively stretched case. When the powder is ignited, the case is expanding in all directions, including front and rear. Brass does have a limited amount of "springback", but when the amount of headspace exceeds the ability of the case to springback, the case will be permanently stretched and weakened. Stretched cases can be easily identified by a bright, light colored ring located just forward of the head. The case at that point has been stretched dangerously thin. Those cases should be thrown away immediately as they will come apart at that point sooner or later. Case head separations can sometimes be very nasty.
This.
An over pressure primer will have a distinctive flattened appearance.
That looks like a primer strike from an old military gun, which tend to have large firing pins and massive springs.
When fired, the pressure drives the primer out slightly, then the recoil slams the brass case into the primer against the breech reseating the primer. If it is high pressure, it will flatten the primer. Many times when you have primers backed out, it is because of low pressure and the case was not driven back into the primer to reseat. I have found this on 30-30 brass frequently. It is a low pressure cartridge when compared to other rifle cartridges.
I am wondering if what happened in your case was the primer was bulged out from firing and the reason it looks cratered as the dimple from the firing pin was also pushed out making it appear to be cratered.
Rosewood
I am wondering if what happened in your case was the primer was bulged out from firing and the reason it looks cratered as the dimple from the firing pin was also pushed out making it appear to be cratered.
Rosewood
Here is an extreme case of overpressure. See how the primer is flattened and what appears to be flowed. Also notice how it fills in the gap around the primer, in your case, it has not done that. I think this one was slightly out of alignment when the case slammed into the primer causing it to look that way. It hit so hard, the tool marks on the breech face left marks on the primer.
Rosewood
Rosewood
Attachments
![20170914_124921[1].jpg](https://theoutdoorstrader.b-cdn.net/data/attachments/1217/1217083-eda48a9c1b57501c46e48731c9c6a04d.jpg)
You know, it would be neat if we could see every step of a cartridge firing as it actually happens, not an animation. If we could see the primer ignite, powder ignite and which direction it burns, how the primer moves in reference to the case and how it impacts the breech. If we could stop it as it occurs and inspect the condition of the components, we could learn a lot.
Rosewood
Rosewood
