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Funky primers. Does anyone know what this is?


NateTheSkate
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So, I was able to get some range time in today,  shooting a 2011 I am building. Everything was going smoothly (more or less, I'm still a bad shot) but when I was policing my brass and I noticed some strange looking primer strikes on my brass...

 

This was factory ammo, Remington according to the headstamp, and was just standard range ammo, not overpressure ammo or hollow points or anything like that. It almost looks like the primer is flowing back into the FP hole, but I wouldn't expect to see that with factory ammo

 

In any event, i'm at a bit of a loss. Any info would be appreciated.

IMG_0081.jpg

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I suspected it was primer flow, but I wouldn't expect to see that on factory ammo I wouldn't think. 

 

I fired some of the same ammo out of a different pistol, and the primer strikes looked more-or-less normal.

 

Could it be a headspace thing?

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An overly large firing pin hole, perhaps combined with a w4eak firing pin spring can be contributors.

 

Have you taken the barrel out and dropped a round into it to see if the bullet may be contacting the rifling?

 

Headspace, for straight wall cases, is more fluid than with bottle-neck cases.  There have been instances where quite short cases have been fired, held only by the extractor, and gave no problem, even though technically the headspace was excessive.

 

The bullet contacting the rifling, or telescoping into the case, or the firing pin stuff mentioned seem most likely.

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The slide is an STI, so I would expect it to be within spec, but i'll dig up my pin gauges and measure the FP hole.

 

I will also check to see if the bullet is being set back by the rifling. If this is the case, what would you suggest I do about it? 

 

I think maybe i'll just not shoot Remington ammo anymore, and see if the problem resolves itself. 

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If the bullet is moving into the case when feeding into the chamber, the bullet tension is not adequate.

 

Bullet tension is a combination of several factors, including bullet diameter, case wall thickness, expander ball diameter and sizing die diameter.

 

I've not heard of it recently, but many years ago Remington 45 Auto cases had thinner walls than others and made it hard to get good bullet tension.

 

If it is not happening with other makes of brass, it may be related to the cases.

 

 

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Could be an instance of extended firing pin, stretching the soft primer cup to the max, then the pressure forcing it back into the firing pin hole, then getting sheared off. Looking at the rest of the primer, the edges are still round, I see no flattening at all, so I don't think it was over pressure...just a super soft primer in conjunction with an extended firing pin.

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17 hours ago, GrumpyOne said:

Could be an instance of extended firing pin, stretching the soft primer cup to the max, then the pressure forcing it back into the firing pin hole, then getting sheared off. Looking at the rest of the primer, the edges are still round, I see no flattening at all, so I don't think it was over pressure...just a super soft primer in conjunction with an extended firing pin.

 

The firing pin is an EGW piece, I don't know if it is considered "extended" or not. I can always measure it I suppose....

 

I think next range trip ill take along some other brands of ammo and see if they do the same thing. I think I have some Speer, S&B and Winchester sitting around, that should make for a good cross-section.

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Are the flash holes normal size? If they are too small it can sometimes push the primer back more even on a light load. I would also take one of those and reload it to see if it does the same thing.

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The perimeter of the primers are nice and rounded, doesn’t appear to be over pressure.  The hits look a little off center, but the interesting thing from the picture is what appears to be cracks in the primer under where it flowed back.  Does the firing pin spring seem normal?  Haven’t heard of problems with Remington primers recently.

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7 hours ago, Why said:

The perimeter of the primers are nice and rounded, doesn’t appear to be over pressure.  The hits look a little off center, but the interesting thing from the picture is what appears to be cracks in the primer under where it flowed back.  Does the firing pin spring seem normal?  Haven’t heard of problems with Remington primers recently.

I don't know what those deformations are, I think they might be from little bits of brass stuck to the breechface. Whatever they are I don't think they are cracks. The mystery deepens....

 

I took out the firing pin and spring, they both look normal. I'll replace the spring, just in case.

Edited by NateTheSkate
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Those look like the firing pin is too short (but obviously long enough to set off the primer) letting the primer flow back into the firing pin hole and/or the firing pin hole looks like it might be oversized or excessively chamfered.  The other marks on the primer look like imprints from debris left on the breachface by the sheared primer flow.

 

Nolan

Edited by Nolan
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Change one thing at a time to isolate the problem. Id change FP spring first. You fired the ammo in another gun. Next step is to fire some different major ammo in the suspect gun.
Id also check next tension on the ammo, Push it against a work bench see if the bullet sets back.
Remington is bankrupt , movin, being sold once again for a reason.

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  • 2 months later...
  • 3 weeks later...

I’m seeing the same phenomenon in my 9mm open 2011. Oddly enough it’s not showing up in my 9mm Czechmate open pistol. 
ive changed the FP spring to a new factory one, with no improvements. Next step is to try factory ammo (I doubt it’s the ammo, but it’s easy enough to test) and then a different firing pin. 

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