Strange primer strike, high pressure? (pics)

Greyhunter

Greyhunter

New member
The last two rounds I fired while out hunting had this appearence. I checked the rounds I fired a couple months ago and this didnt happen. It was around 80* then, the round in the pic was fired at around 20*.
Is this caused by high pressure, possibly a dirty chamber (causing the high pressure)? I suspect that because a couple rounds lately have been slightly difficult to eject manually and after watching the Brownells video I see that I have not been effectively cleaning the chamber.

The round is a 60gr Vmax over 24gr of Benchmark, primer is CCI 400, Win brass full length sized in a Redding die. Rifle is a RRA Predator pursuit, with about 175 rounds through it total.

Thoughts?

primer.jpg
 
I wouldn't think it's from high pressure because the primer is still very round. But I have never seen that kind of mark before.
 
Poor fit of the firing pin to the bolt. Either the pin is too small or the hole in the bolt is too big. Definitely not high pressure.

Jack
 
Well Greyhunter

Your load does not seem hot. My hornady manual lists 25 grains of benchmark as a max with a 60 grain v max in 223.

I would make sure you are pushing the shoulder back far enough but not too far.
If you don't have a case length guage I would recommend one.
When you say the rounds are "difficult to eject manually" that leads me to believe that the shoulder is too far forward and the rifle is not going fully into battery.

Good luck
 
I wouldn't say that shows any signs of high pressure. The primer is still showing a radius edge like a new one with little or no flattening and I can't see any extractor marks embossed into the brass.
The raised area around the firing pin is from a poor diameter match between the firing pin and the bolt, as mentioned above. Hard to say whether that would develop into a problem as pressure went up or not.
I think you're good to go, personally.
 
Quote:
Poor fit of the firing pin to the bolt. Either the pin is too small or the hole in the bolt is too big. Definitely not high pressure.

Jack



Jack,
What would cause this to suddenly occur? Previous rounds did not do this.

EDIT: Would just cleaning the bolt and firing pin correct this?
Thanks
 
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Quote:
Well Greyhunter

Your load does not seem hot. My hornady manual lists 25 grains of benchmark as a max with a 60 grain v max in 223.

I would make sure you are pushing the shoulder back far enough but not too far.
If you don't have a case length guage I would recommend one.
When you say the rounds are "difficult to eject manually" that leads me to believe that the shoulder is too far forward and the rifle is not going fully into battery.

Good luck



All the brass was sized at the same time, and previous rounds fired did not exibit this condition, so I dont know why they wouldt all do it if it were a sizing problem?
Unfired rounds were not overly difficult to eject, but I noticed it was harder than it should be and some cases were dirty. No doubt the chamber needs a good cleaning and I think that will cure the ejecting difficulty. Everything ejects fine when fired.

I appreciate the opinions so far.
 
thought I would run this by you guys, could it be, the long throat of the wylde chamber, combined with the lower temps slowing powder burn down enough to cause an under pressure issue? after the bullet makes that kind of jump as pressure builds, that does increase case capacity a good bit for a 223 cartridge.
the mark appears as if the primer cratered, then was pushed against the bolt as pressures peaked.
RR
 
Firing pin diameter v. boltface diameter is one visible symptom. Headspace could be an issue. If you have a Stoney Point head and shoulders gauge, you can compare your fired rounds to you sized (but unfired) rounds and see how much you are setting back the shoulders.

Could also be that the case was not able to 'grip' the chamber wall due to lube in the excess lube in the chamber.

Were these the first two rounds fired after a cleaning? I've seen that before. Does the brass now have a few spots on it that look like corrosion?
 
You said that it did not happen a couple of months ago. Were you using mixed brass then, or just winchester. There can be pressure differences between different brands of brass.

Try going to a thicker cup primer such as the CCI 450, Rem 7 1/2, or the CCI BR-4.
 

This is the classical appearance of a fired primer in a rifle without enough support of the firing pin.

It is not a hot load, and it has nothing to do with head space, dirty chamber, case length or anything else.

The rounded edges of the outer edge of the primer show that the pressure is well within normal limits, and also show that there are no headspace issues.

The rounded edges of the pin impact are classical of the pin either being too small for the pin hole (which would not apply here since it just started showing up)...

... or the pin/spring is not able to restrain the case pressure, the primer metal is being pushed back out of the pinhole. This not the same as classical cratering, because the pressure is so low, and the edges of the pin area are rounded.

I would strip the bolt and clean everything and make sure the spring is up to snuff.

Wouldn't hurt to clean the whole rifle on general principals.

primer.jpg
 
Since the AR doesn't have a firing pin spring, I would think MPFD could be right about the hammer spring. If there is anything blocking the hammer or firing pin from going all the way forward, it could be the problem. Stipping the bolt and making sure there is no gunk inside to limit or jam up the firing pin would be the first thing I would try. With the bolt out of the rifle, make sure the firing pin will extend all the way through the bolt face. As the other guys have said, it's not any kind of a pressure problem. A dirty chamber can cause extraction problems so clean and polish it. It does look as if the firing pin has been pushed back into the bolt, or never fully extended through the bolt face, and the primer was extruded into the pin hole in the bolt face.
 
check for excessive oil/grease/lube in the firing pin area. The cold weather may have 'jelled' the oil an slowed the firing pin.
 
Man, I like tator tots! /ubbthreads/images/graemlins/smiliesmack.gif
Frankly head spacing, shoulder angles, etc, are over my head, but I'm leaning towards the last few responses regarding the dirty bolt and excess lube causing a problem in the cold. The barrel was cleaned in Sept and only fired twice before these two rounds. However I did dump plenty of oil in the bolt without otherwise stipping or cleaning it, and that may be the problem with the cold temps. The trigger is a 2 stage RRA NM which was reduced to around 2.75lbs by Dtech (presumably using a lighter spring), and the cold oil combined with the lighter spring sounds like the prime suspect to me. (no fault of Dtech's btw, trigger is beautiful)

As noted the chamber also needs proper cleaning and I'm planning to drop by Brownells tommorow and pick up some chamber swabs to go with my chamber brushes and take care of that issue.

BTW, both rounds killed the coyotes they were pointed at, and the two before that killed coons (but I couldnt find the brass). /ubbthreads/images/graemlins/grinning-smiley-003.gif

I really appreciate the education and I will update if the cleaning doesnt solve the issue.
 
If you lube it with Dri-Slide after cleaning it won't freeze up again. Not that it froze up last time, but it looks like it was close.
 
Just to update my post, I cleaned the bolt carrier group up and it seems to have stopped the problem. There was a TON of dirty oil on the firing pin. The cleaning removed all traces of oil so I did have to re-apply oil but tried to use less. Only one of the 5 rounds I have fired since showed this primer strike and it was less noticable.
As for the unfired rounds being somewhat hard to eject, it seems to be limited to my most recent handloads only, so its a case issue and not an issue with the previously dirty chamber. Not sure what is causing it, but it isnt the gun.

Thanks for the help.
 
You can't verify this unless you play with seating a few rounds a little deeper than normal. I think the bullet was pushed into the case and thus changed the pressure.

Neck tension if your not using crimped ammo.

I know, I know, I don't crimp either.
 
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