Pierced Primer

[Hinnerk]

I have been working on my Ishapore SMLE No.1 MkIII and experienced a pierced primer for the first time. Attached is a photo showing the pierced example with other fired rounds. So far I have put 105 rounds through this rifle; 5 factory rounds and 100 hand loads. The cases shown here were fired previously with -013 O-ring ahead of the rim to form the shoulder to the chamber and then neck sized only. This time around I fired some rounds with O-ring and some without. Without, the primers backed out about 0.010". With, the primers were flush. The factory rounds were fired without O-rings and the primers did not back out. Handloads used NOE 314-202 cast lead projectiles sized to .314 and, in this series, WLR primers and 21.5 gr IMR 4227. I don't think this is a hot load and I don't think this is the cause of primers backing out or the pierced primer.

What is obvious is that the firing pin strikes the primers off center. I am not sure why this is. Perhaps because the very strong extractor claw spring is pushing the bolt head aside? The SMLE uses rear locking lugs and so this seems a possibility. I am guessing that the pierced primer was caused primarily because of off center strike.

Any thoughts, especially from those with SMLE experience?

[JagerDog]

Is that pierced or out gassing up the side?

[Hinnerk]

Is that pierced or out gassing up the side?

Looked to me pierced but the hole was in the side of the indentation. I've already decapped all the cases but I should probably save the pierced primer and some other examples for forensic purposes. I also still have the cases indexed in the box so I can double check about your question.

[fguffey]

You do not have a pierced primer. The pierced primer is caused by a balance between the firing pin spring and pressure inside the primer. You do have another problem with the .010" protruding primers.

F. Guffey

[God Bless America]

One of those primers, is not like the other....

The sooty one is flat, given the low pressure shown on the others, I would check the flash hole in that case. You may also have overcharged that one with 4227.

To fireform, Ackley recommended a 'good, snappy load.' I recommend trying a few with the O-ring and a mid-range, full-power rifle load. That should better fireform your case, preventing primers from backing out when reloaded.

As for the off-center primer strikes, I might look into a different bolt head. That would bother me a lot.

[Hinnerk]

One of those primers, is not like the other....

The sooty one is flat, given the low pressure shown on the others, I would check the flash hole in that case. You may also have overcharged that one with 4227.
....

I did notice that it looks flatter than the others. I did visually check all cases after filling. Also, they were all weighed out one by one using a scoop, trickler and balance. Still, I suppose that something could have gone wrong there. Will take a close look at that case. I did use a flash hole tool on all these cases at the start so I don't expect to see anything strange there (malformed or blocked).

[JagerDog]

IME backed out primers indicates too low of pressure (or an abundance of headspace)...the brass isn't expanding to conform to the chamber.

[pacrat]

This time around I fired some rounds with O-ring and some without. Without, the primers backed out about 0.010". With, the primers were flush. The factory rounds were fired without O-rings and the primers did not back out.

I don't think this is a hot load and I don't think this is the cause of primers backing out or the pierced primer.

Yes these are low pressure loads.
Yes they are causing backed out primers.
With exception of those fired with O-rings. The O-rings served to hold the cartridge base against the bolt face. So the primers couldn't back out. That is why those without O-rings backed out.

The pierced primer is a different issue. It show signs of being higher pressure than the others. But it is possible, that it was faulty. Thinner or softer cup. One primer out of 105 is not a viable indicator. But does make the possibility a probability.

You definitely need to beef up your load a bit to properly fireform your shoulders. Use the O-rings until you get the case dim to match the bolt to datum dim.

JM2c

[Redemption]

it is weird that you would get a partial primer blow out and a flattened primer cup on a low pressure load.

It would seem to me that the one case is exhibiting signs of high pressure conditions... or I guess a weak primer cup...

Could be that the off center strike caused the cup to be weakened enough to allow for a blowout?

How positive are you that it wasnt a hot round?

[Hinnerk]

I had a close look at the primer from and primer pocket on the offending case. There is no evidence of gas leakage between the primer and the walls of the primer pocket. The gas blew through a hole on the outward side of the striker dimple. I am supposing that with the strike so close to the periphery, the striker/firing pin sheared the brass cup of the primer, causing the hole.

I think that it is virtually impossible that this was a double charge and I cannot explain by any observation how I could have gotten more than a few tenths of a grain of additional powder in that case. IMR 4227 is cut very short and I can imagine that a granule of two could get into the flash hole or maybe even into the primer pocket. I have no idea whether something like that could account for a flattened primer. It doesn't seem likely to me.

I took measurements of the case head to shoulder distance on 15 cases each of the O-ring and non O-ring instances and it is plain that the cases had not had their shoulders blown all the way forward with the previous loads. The difference seems to be about the same as the amount the primers backed out.

[TexasJackKin]

I had a close look at the primer from and primer pocket on the offending case. There is no evidence of gas leakage between the primer and the walls of the primer pocket. The gas blew through a hole on the outward side of the striker dimple. I am supposing that with the strike so close to the periphery, the striker/firing pin sheared the brass cup of the primer, causing the hole.

That's the first thing I thought when I looked at the picture.

[Redemption]

crazy... never seen anything like that then.

[tonyjr]

Years ago I have a lot of problems with primers . Pericing , falling out , bending -
I started using only CCI - they are a little thicker and seem to seat better . But , that was years ago .
I would send the picture to company - you may have a bad / bent firing pin .
Since you are using cast load , are you sure that one was sized ?
I run my 44 nd 50 AE FMJ thru a sizer , but I have plenty of help , so time is not a problem . [ I don't bother with other pistol / rifle rounds ]

[Hinnerk]

I have some CCI, S&B and other primers on hand that I can try as alternates but I agree that I need to have a closer look at that firing pin and try to understand what is causing the off center strike. This is an old rifle (Factory Rebuilt in 1940 and earlier manufacture markings were scrubbed). After much work on the stock (repairs and refinishing) I finally got around to trying it out this year. I did completely tear down the bolt for cleaning and inspection when I did the earlier work. I didn't notice anything unusual about the firing pin tip at that time.

Yes, I am sure that all the projectiles were sized. Actually, there wasn't anything noteworthy about that particular load other than I noticed the gas coming out the side of the action when it was fired. Projectile hit the target. Felt recoil was same as the rest (light).

As I mentioned yesterday, I took some measurements on some of the fired cases; 15 each of the O-ring and non O-ring examples:

With O-ring:
Average case length after firing: 2.207" (s=0.002")
Average head to .375 datum on shoulder: 1.859" (s=0.001")

Without O-ring:
Average case length after firing: 2.209" (s=0.002")
Average head to .375 datum on shoulder: 1.851" (s=0.001")

s is standard deviation

The case with the pierced primer was fired without O-ring. It measured:
Case length after firing: 2.206"
Head to .375 datum on shoulder: 1.850"

I did not trim this brass at any point in its life.

[tonyjr]

Anneling helps brass fire form .
That case could have been wiped down with brasso to make shinny . Brasso has amonia in it that makes brass hard - then it does not seal when fired .
Keep posting what you find .