357 primer problem

[Wyatt Smith]

I was working up for my 357 with 158 grain XTPs and H110 today. I worked up to 15 grains where I found my best accuracy and lowest SD.
When I was done I noticed a few of my primers were dark in the dent from the firing pin. It looks like to me that a small hole is getting burned through the primer. The firing pin seems to have a small divot in it.
As I was testing I noticed one of my chambers was about 100 fps slower that the other five. I wonder if that is related.
I don’t think it is a pressure problem, because it happen on the starting loads as well as my cast bullet 900 fps plinking loads.
Any help would be appreciated.

 

[Wyatt Smith]

 

[shootist~]

No idea really, but the Starline brass I have used recently (just 3006) was unusually brittle until annealed.

I suggest different brass and same primer to see if it's possibly a brass issue.
Or: Changing to a small rifle primer. (Only thing I used back in my IMSHA/ 357 days - with a very hot load of 296 and 196 gr hard cast with gas checks).

 

[Monsai52]

What gun are you firing these from.

Best regards,

 

[Wyatt Smith]

What gun are you firing these from.

Best regards,

Ruger Blackhawk 3 screw.

No idea really, but the Starline brass I have used recently (just 3006) was unusually brittle until annealed.

I suggest different brass and same primer to see if it's possibly a brass issue.
Or: Changing to a small rifle primer. (Only thing I used back in my IMSHA/ 357 days - with a very hot load of 296 and 196 gr hard cast with gas checks).

I will try that thanks.

 

[Bob Nelson 35Whelen]

I was working up for my 357 with 158 grain XTPs and H110 today. I worked up to 15 grains where I found my best accuracy and lowest SD.
When I was done I noticed a few of my primers were dark in the dent from the firing pin. It looks like to me that a small hole is getting burned through the primer. The firing pin seems to have a small divot in it.
As I was testing I noticed one of my chambers was about 100 fps slower that the other five. I wonder if that is related.
I don’t think it is a pressure problem, because it happen on the starting loads as well as my cast bullet 900 fps plinking loads.
Any help would be appreciated.

@Wyatt Smith
What primers are using y oung mister Smith. May be try a harder primer like a small rifle primer. That indent in the primer looks a bit big to me. Are you taper or foll crimping as this can affect pressure if not consistent.
Bob

 

[marksman]

you can see there is no pressure,
l would be looking at the firing pin but maybe primers

 

[TOBY458]

Make sure they're small pistol magnum primers, or small rifle primers. I loaded some small rifle primers in my 357 recently, and they work well. My load is a 140gr Lehigh bullet over 18gr of H110. So I think your loads should be ok as far as pressure is concerned.
One thing to look at is, sometimes a revolver has pretty sloppy "headspace", so the cartridge will slam back against the frame of the revolver when fired. This will cause the primers to look dished or flattened. I would suspect a cracked primer could be caused by this same problem, but I've never seen it.

 

[Wyatt Smith]

They are Remington small pistol primers. I ordinarily would use magnums, but can’t find any. I will try some small rifle primers.I’d always heard they were too hard, but I have never tried them.
The firing pin does have a small mark on the end of it. I am going to try to find one.
Thanks.

 

[Opposite Pole]

These primers are round and don’t look to have been subject to excessive pressure. To me they look like very mild loads. So I’d be guessing a primer of firing pin issue.

 

[fourfive8]

Aside from the obvious, like excessive pin protrusion, it'd be worth looking at everything possible.

These types of issues can be hard to diagnose! Since we are exploring all possibilities.... you might check cylinder lash... aka end play. I assume this is a revolver with cylinder? A little too much end play can show symptoms similar to those of excessive headspace. The hammer falls, pin hits primer, primer fires and forces case forward away from breech (frame) face, the primer is partially unseated, the cartridge comes up to full pressure and forces case rearward reseating primer and introducing increased deformation force of pin into primer. In this case a little too much, perforating primer and letting gas escape causing the carbon smudge in the pin crater. Dunno... just another possibility.

Primer cup dimensions are different between pistol and rifle primers. Even if they fit with correct snugness, IIRC, rifle primers are slightly taller than pistol primers. That may or may not introduce another unwanted variable??

 

[Wyatt Smith]

In this case I could go out too the shop and get a set of feeler gauges to check my headspace, right? Just check between the case and the breech face?

 

[Monsai52]

Looks like pierced primers. Remove the cylinder, cock the hammer and push the firing pin all the way forward and check the extension past the recoil shield. It's either an out of spec firing pin, or way soft primers, or a combination of a bit of both.

Best regards,

 

[crs]

Reminds me of how primers looked when fired in my M1892 .357 rifle. Especially when I had been shooting hot loads. Eventually one would smoke, so off the rifle went to a gunsmith.
In my case, the firing pin was too thin or the hole the pin protruded through was too big and the primer could flow back around the tip of the pin. The rifle smith did his magic and all has been well since. I also stopped shooting hot loads in the rifle. Factory .357 is hot enough from a 20 inch Douglas barrel.

 

[TOBY458]

Aside from the obvious, like excessive pin protrusion, it'd be worth looking at everything possible.

These types of issues can be hard to diagnose! Since we are exploring all possibilities.... you might check cylinder lash... aka end play. I assume this is a revolver with cylinder? A little too much end play can show symptoms similar to those of excessive headspace. The hammer falls, pin hits primer, primer fires and forces case forward away from breech (frame) face, the primer is partially unseated, the cartridge comes up to full pressure and forces case rearward reseating primer and introducing increased deformation force of pin into primer. In this case a little too much, perforating primer and letting gas escape causing the carbon smudge in the pin crater. Dunno... just another possibility.

Primer cup dimensions are different between pistol and rifle primers. Even if they fit with correct snugness, IIRC, rifle primers are slightly taller than pistol primers. That may or may not introduce another unwanted variable??

Small rifle primers and small pistol primers are identical in size. I use them in my own 357 mag. I believe the cups are indeed taller on Large Rifle primers vs Large pistol primers though. The main difference between small rifle and small pistol primers is cup hardness. My S&W lights them just fine. I ran out of small pistol magnum primers, so I had to do this out of necessity. Glad I had some small rifle primers on hand and no small rifle to shoot them in! LOL!

 

[JimP]

There is really no problem with headspace with revolvers that use rimmed cases. That is where you can use 38 Specials in a 357 mag, or if you have a 357 Maximim you can shoot 357 mag and 38 Specials in the same cylinder

 

[fourfive8]

Here's the SAAMI chart for primers and pockets as provided by Sinclair

The rim of the case does control the headspace relative to the cylinder/chamber in a revolver. But excessive cylinder end play can create a situation causing similar issues to excessive headspace in a closed breech chamber.

 

[Jörg Krüger]

Don't know if this was suggested, but don't you have some other ammo with different primers to try?
Quickest way too determine if it is problematic primers or a problematic firearm. Should steer you in the right direction.

 

[Wyatt Smith]

Don't know if this was suggested, but don't you have some other ammo with different primers to try?
Quickest way too determine if it is problematic primers or a problematic firearm. Should steer you in the right direction.

I did fire some factory ammunition through it. None of the primers were pierced. I think I can get this one ironed out with not too much trouble.

 

[Jörg Krüger]

I did fire some factory ammunition through it. None of the primers were pierced. I think I can get this one ironed out with not too much trouble.

There we go, problem solved