Cratering on primers

[jds holler]

I kind of look at cratered primers as just one piece of evidence that I might have high pressure. The other evidence would be extreme flattening, ejector swipe, tight bolt lift, chronograph says high fps --

Without any other evidence, cratered primers don't mean much. jd

 

[Bora72]

Have your bolt firing pin hole bushed. Problem solved. See Carlsbad, he's the man.

Hello,
I live on Italy, here have some gunsmith and the costs are too crazy.
But I don't think that are a common work here...

 

[Bora72]

GTG = Good To Go

Good to go like 15 o more firing?

 

[Bora72]

He's in Italy, stuck with Europe gunsmiths.

Unfortunately for the gunsmithing side...

 

[Bora72]

I kind of look at cratered primers as just one piece of evidence that I might have high pressure. The other evidence would be extreme flattening, ejector swipe, tight bolt lift, chronograph says high fps --

Without any other evidence, cratered primers don't mean much. jd

The gap from the pin and hisnhole and the free bore are the cause by my think

But the photo of the primers.
Left 35gn and 139 Scenar
Right 36,5gn and 120 ppu

 

[SeabeeKen]

The gap from the pin and hisnhole and the free bore are the cause by my think

But the photo of the primers.
Left 35gn and 139 Scenar
Right 36,5gn and 120 ppu

I dont believe its a pressure problem. Enjoy

 

[Bora72]

I dont believe its a pressure problem. Enjoy

I think the problem are the inertia pressure.
The next trip to the range I make the same load but with more freebore

 

[SecondsCount]

The question is being asked as to why one of the loads has signs of higher pressure, not how to fix the cratering, etc.

I did some testing in GRT. The 139 Scenar load has a greater seating depth and increases pressure around 1000 psi.The loads are in the low 40K range, well under what the cartridge is capable of.

Gun companies need to understand the important of using a small firing pin when chamber for a cartridge that uses a small primer.

 

[Bora72]

The question is being asked as to why one of the loads has signs of higher pressure, not how to fix the cratering, etc.

I did some testing in GRT. The 139 Scenar load has a greater seating depth and increases pressure around 1000 psi.The loads are in the low 40K range, well under what the cartridge is capable of.

Gun companies need to understand the important of using a small firing pin when chamber for a cartridge that uses a small primer.

Hello, unfortunately every company make some choices, sometime this choice result the choice of the century, some time Renault the bad choice of the century....

If I find one gunsmith on my country that cam make the mod for a rasonable cost I ask if can change also the large firing ping with a small version

 

[NorCalMikie]

Primer cratering is a product of the firing pin hole in the bolt face generally being to large and having a loose fit to the pin diameter and possibly having a chamfer. Bushing the bolt face and reducing the firing pin to 0.062 fixes this????

How bout a simple headspace issue?? NOT barrel/chamber firing pin bushing issue problem BUT, brass too short for the chamber? Round goes BANG, brass moves back in the chamber and the primer gets "cratered". And you never have to think about bushing the firing pin AND, you can spend those extra $$$ not spent on reloading components. Do the easy stuff first.

 

[William Vogel]

How bout a simple headspace issue?? NOT barrel/chamber firing pin bushing issue problem BUT, brass too short for the chamber? Round goes BANG, brass moves back in the chamber and the primer gets "cratered". And you never have to think about bushing the firing pin AND, you can spend those extra $$$ not spent on reloading components. Do the easy stuff first.

He claims that the brass fits the chamber and that the bullets being really close to jam is causing a pressure spike. So if the brass fits then it’s back to the firing pin fit to the firing pin hole. I’ve been in this situation. Reducing pressure will alleviate the craters but it doesn’t appear that there are any additional pressure signs.

 

[47WillysGuy]

The gap from the pin and hisnhole and the free bore are the cause by my think

But the photo of the primers.
Left 35gn and 139 Scenar
Right 36,5gn and 120 ppu

I had a Remington 700 bolt bushed because of some serious cratering. No more!
Firing pin bore - 0.0609"
Firing pin diameter - 0.0593"
Difference - -0.0016"

That's .0008" on a side.
Recommend a comparison of your bolt/firing dimensions to see what your difference is! Shoot small!

 

[Bora72]

I had a Remington 700 bolt bushed because of some serious cratering. No more!
Firing pin bore - 0.0609"
Firing pin diameter - 0.0593"
Difference - -0.0016"

That's .0008" on a side.
Recommend a comparison of your bolt/firing dimensions to see what your difference is! Shoot small!

Hello, I take some measures when came back to my house.
Thanks so mutch for the advice and your measures.

 

[boltfluter]

The gap from the pin and hisnhole and the free bore are the cause by my think

But the photo of the primers.
Left 35gn and 139 Scenar
Right 36,5gn and 120 ppu

If you are not piercing primers and cases extract ok, it is a non issue. Excessive headspace, as you have mentioned, will definitely contribute to this, giving a false indication of trouble when there really is just a reloading problem. I have several rifles in different BR configurations that kick up a nasty burr with their favorite loads but never pierce the primer. Extraction is fine so I just go on shooting them and life is good. I reload them with Varget, 105 VLD, and a brand new CCI-450 and blissfully carry on shooting. Lol.
Paul

 

[Bora72]

If you are not piercing primers and cases extract ok, it is a non issue. Excessive headspace, as you have mentioned, will definitely contribute to this, giving a false indication of trouble when there really is just a reloading problem. I have several rifles in different BR configurations that kick up a nasty burr with their favorite loads but never pierce the primer. Extraction is fine so I just go on shooting them and life is good. I reload them with Varget, 105 VLD, and a brand new CCI-450 and blissfully carry on shooting. Lol.
Paul

Hi Paul, I don't have excessive head space, my head space setting are .002" from a fired case.

My curiosity are about why one have cratering with low charge and another no with more powder on the load.

No reloading issue for my load.

Regards

 

[6BRA]

Case Capacity variance? Case lube still on case when fired? Cratered primers really don't interest me. A pierced primer would.

 

[Bora72]

Case Capacity variance? Case lube still on case when fired? Cratered primers really don't interest me. A pierced primer would.

Hello, same case capacity.
No lube residue on the case, i dry tumble the brass after sizing, and after seath the bullet clean the ammo with the isopropil alcool.

 

[chop house]

I was working with 6 br and tried fiocchi srp on a whim. Stopped after the second shot and pulled the rest. They were not high pressure loads, but still cratered.

 

[Old Navy]

The gap from the pin and hisnhole and the free bore are the cause by my think

But the photo of the primers.
Left 35gn and 139 Scenar
Right 36,5gn and 120 ppu

I don't see enough crater there to even be talking about.

 

[Bora72]

Hi, aside from what each of us can see and interpret from the photo or give a meaning to the word "cratering," the behavior on the two primers is markedly different and the opposite of what should be seen based on the reloads used.
So my post is out of curiosity to know and understand why this happens.
Each of us here can do as we wish, but that doesn't fall within what was posted in the opening message and subsequently reiterated several times.

Best regards