Armory Sponsor
Posted: 10/1/2013 1:26:57 PM EDT
|
Not sure what the cause of the pierced primers are. Internet search brings up various reasons, so I wanted to get y'alls opinion.
Rifle is a 16" CMMG with about 800 rounds through it. Firing pin looks fine. Brass is various fired PMC with Winchester SR primers. Load is 24gr of IMR 8208xbr (well below Hornady manual max) over a 55gr bullet. All primers were set below flush. I've shot about 90 rounds today, and these two were the only ones who had this issue. Just curious about what might have caused this. Left to right: normal primer strike, deep firing pin strike, pierced. 
|
|
Quoted:
Did you swage / ream the primer pockets? The one on the left doesn't look like the primer was ever swaged, but the other two do. Maybe the primers in the two on the right weren't seated deep enough? They were swaged. And the primer depth was checked properly. |
|
Quoted:
Be sure to take a close look at your firing pin, look for pitting/sharp edge. Case on right looks like a primer failure. How many did you shoot of this batch with these 2 failures? eta, how many firings on those cases? 90 rounds today. These are some of my first .223 reloads from about a year ago, so some of the brass may not have been crimped. Unfortunately, my notes sucked back then. The crimped cases are x1. |
|
My reason for wondering about the two cases on the right was that if they hadn't been swaged / reamed, the primers may have been proud, or may have gathered metal as they were seated.
A primer that seats with some effort can indicate either the primer pocket is on the tight side, or you are broaching metal as it seats. |
| Were the other 800 rounds loaded with Winchester SR primers? Or just these in the photo? Loose primer pockets is my guess. Edit/add- Far right brass-When the pocket is loose, gas will leak between the cup & brass, sometimes even putting a pock mark in the bolt face. The leak & a defective primer cup look the same. The middle brass, the pierced primer backed out of the pocket on firing, because of the loose pocket. This happens when there is more head clearance than needed. (cartridge slop/loose fit in the chamber). Pierced can be from a rough, or defective firing pin nose also. Photo Link |
|
Loose primer pockets is my guess. Exactly. A primer going in an unswaged pocket may feel tight, but in reality the primer is broaching the primer pocket and it will be loose. Deprime the cases, keeping the primers with their respective cases, and look for signs of galling. |
|
What bullet are you shooting, and to what depth are they seated?
I had this issue when shooting 55gr Hornady SP & Winchester SR primers. Turns out I did not have the bullet sat deep enough in the case, and this was causing overpressure, therefore piercing the primers. |
|
Just bought 4k winchester SRs- I hope this issue is sorted out.
Perhaps you are loading either too long or too short and spiking pressure too high? I have be loading with rem 6 1/2s for some time (not recommended) with no rupture problems, although they do flatten. |
|
Quoted: What bullet are you shooting, and to what depth are they seated? I had this issue when shooting 55gr Hornady SP & Winchester SR primers. Turns out I did not have the bullet sat deep enough in the case, and this was causing overpressure, therefore piercing the primers. |
|
Quoted:
This won't cause excessive pressure. Quoted:
Quoted:
What bullet are you shooting, and to what depth are they seated? I had this issue when shooting 55gr Hornady SP & Winchester SR primers. Turns out I did not have the bullet sat deep enough in the case, and this was causing overpressure, therefore piercing the primers. Hmm. I was under the impression if you had the bullet jammed into the lands, pressure would spike? Maybe I'm wrong. 
|
|
Quoted: Hmm. I was under the impression if you had the bullet jammed into the lands, pressure would spike? Maybe I'm wrong. Quoted: Quoted: Quoted: What bullet are you shooting, and to what depth are they seated? I had this issue when shooting 55gr Hornady SP & Winchester SR primers. Turns out I did not have the bullet sat deep enough in the case, and this was causing overpressure, therefore piercing the primers. Hmm. I was under the impression if you had the bullet jammed into the lands, pressure would spike? Maybe I'm wrong. You can't do that with an AR. (mag length) The throats are long also. The 55 gr bullet is short, doubt you could seat it long enough to do this in an AR. Maybe more info would help.
|
|
Quoted:
If you do that yes. You can't do that with an AR. (mag length) The throats are long also. The 55 gr bullet is short, doubt you could seat it long enough to do this in an AR. Maybe more info would help. Quoted:
Quoted:
Quoted:
Quoted:
What bullet are you shooting, and to what depth are they seated? I had this issue when shooting 55gr Hornady SP & Winchester SR primers. Turns out I did not have the bullet sat deep enough in the case, and this was causing overpressure, therefore piercing the primers. Hmm. I was under the impression if you had the bullet jammed into the lands, pressure would spike? Maybe I'm wrong. You can't do that with an AR. (mag length) The throats are long also. The 55 gr bullet is short, doubt you could seat it long enough to do this in an AR. Maybe more info would help. Makes perfect sense, actually. Thanks for the correction. |
|
Every primer has either a pierce or a tit in the center where it's about to let go. The primer on the right failed at the edge.
All are signs of high pressure. 24 grains is not a low pressure load with a 55 grain bullet and the primers may be the weak link in this combination. |
Armory Sponsor