Different pressure signs from two guns

[Anakin]

Hello, I recently bought a brand new Bergara B14 chambered in 30-06, after testing both factory winchester ammo and my reloads in the range I found different signs of pressure on the primer from shooting my model 70.

Fired primer from Bergara shows signs of excessive pressure but they are normal from model 70. Identical ammos, my reloads use lowest powder loading, so it should be my B14's problem, please see the attached pics(B14 on the left, M70 on the right), my reloads use Hornady cases.

 

[jlow]

Honestly, I am always concerned when someone states "my reloads use lowest powder loading" - you could be too low...

 

[dmoran]

^^^^ +1.... me to

 

[RonAKA]

That primer that has the cratering does not look very flattened. I wonder if it is possible it that gun has excessive clearance between the bolt and the firing pin.

 

[shoot4fun]

It actually could be just the difference in firing pin strike and not a pressure sign.
You don't seem to be flattening those primers; just making different impressions in them with each gun. You could measure the two fired cases from base to shoulder with a Hornady or similar comparator tool. You might see more "headspace" in one than the other as well.

 

[Bart B.]

Slug the bores with 31 caliber round lead balls. Measure them with a good mic to see which one has the tightest groove diameter.

Winchesters are known to have larger groove diameters. They had Western Cartridge Company make .309"'diameter match bullets for Win 70 match rifles with .3085" groove diameters.

 

[johnfred1965]

Could be as simple as an oversize firing pin hole. Search for "bushing the firing pin" in these threads and you should get a wealth of information.

Sorry RonAKA, I read your post, guess it didn't register before I started typing

 

[Anakin]

Honestly, I am always concerned when someone states "my reloads use lowest powder loading" - you could be too low...

Sorry I don't understand how low powder loading could result in sign of high pressure, could you explain further? Thanks

 

[Jet]

Other than the cratered primer the case looks fine. Did you experience stiff bolt lift? Measure a few areas of the case to see how it expanded and compare it to the other case. Likely just a firing pin hole in your bolt that needs some attention.

Rich

 

[jlow]

Sorry I don't understand how low powder loading could result in sign of high pressure, could you explain further? Thanks

This is a well known potential problem that have been discussed many times. Do a search using Google with the key words "Light loads explosion".

 

[RonAKA]

This is a well known potential problem that have been discussed many times. Do a search using Google with the key words "Light loads explosion".

Some years ago I had damage from light loads in my 264WM. Hodgdon had interchanged the 140 grain and 160 grain loads on their web site (and still does have them interchanged), and when I used the lightest recommended H4831 loads I got what is shown in the picture below. I don't recall any signs of high pressure like flattened or cratered primers though. I think what happened at least in my case was that the neck does not expand and seal. The expanding gases leak back around the case and when the pressure outside exceeds that inside the case collapses in. There is the issue of "detonation" and I recall there is a lot of discussion as to whether it really happens or not. All I know is that after I corrected my loads, my issue went away.

 

[gotcha]

Also interesting to note how far off center the F/P strike is on both rifles with Mod. 70 being the farthest off center. Nothing to do with over or under pressure just an observation ....

 

[Rsadams]

That primer that has the cratering does not look very flattened. I wonder if it is possible it that gun has excessive clearance between the bolt and the firing pin.

+1 on this.. If you zoom in you can see how rough the primer looks after bolt face contact... What kind of primers are the silver ones...

 

[Rsadams]

Some years ago I had damage from light loads in my 264WM. Hodgdon had interchanged the 140 grain and 160 grain loads on their web site (and still does have them interchanged), and when I used the lightest recommended H4831 loads I got what is shown in the picture below. I don't recall any signs of high pressure like flattened or cratered primers though. I think what happened at least in my case was that the neck does not expand and seal. The expanding gases leak back around the case and when the pressure outside exceeds that inside the case collapses in. There is the issue of "detonation" and I recall there is a lot of discussion as to whether it really happens or not. All I know is that after I corrected my loads, my issue went away.

Wow never seen this.. Thanks for posting....

 

[danny]

Could be as simple as an oversize firing pin hole. Search for "bushing the firing pin" in these threads and you should get a wealth of information.

Sorry RonAKA, I read your post, guess it didn't register before I started typing

I tend to think along these lines right now too. I think that the OP could also look carefully for a chamfer on the edge of the firing pin hole. I had a Remington SPS Varmint that got cratered primers from a chamfered firing pin hole when shooting normal pressure loads.

Danny

 

[jlow]

Or one of the rifles have some lube in the chamber, that might just be enough to give you pressure signs.

 

[MagnumManiac]

I see this often, it has nothing to do with pressure.
If you take a magnifying glass and look closely at the firing pin hole, I will bet that there is a bevel on it, the primer flows into this bevel and 'craters'.
If it poses a problem, as hard bolt lift, have a gunsmith bush the firing pin hole back to square.
I see this on Rem 700's nearly every other day.

Cheers.

 

[danny]

I see this often, it has nothing to do with pressure.
If you take a magnifying glass and look closely at the firing pin hole, I will bet that there is a bevel on it, the primer flows into this bevel and 'craters'.
If it poses a problem, as hard bolt lift, have a gunsmith bush the firing pin hole back to square.
I see this on Rem 700's nearly every other day.

Cheers.

That is what I am also thinking. My Remington 700 SPS Varmint (17 Fireball) is like that and has cratered primers from day one on all loads.

Danny

 

[fguffey]

Sorry I don't understand how low powder loading could result in sign of high pressure, could you explain further? Thanks

I do not shoot reduced loads, I shoot minimum loads/maximum loads and everything in between. I do not load anything that could be considered 'cute', a cute load could be a reduced load that would allow the bullet to seat into the lands before the powder behind the bullet could get to serous. I know, what does the bullet seating into the lands have to do? If the primer launches the bullet into the lands the bullet will stop; to me there is nothing entertaining about jamming a bullet into the lands and have to wonder if the bullet is going to get a restart before the powder burning pressure gets serious.

There was a shooter/reloader that rendered his 257 Weatherby to scrap, he claimed he only shot reduce loads and then 'proclaimed'; "It must have been a double charge". He posted a picture of his 257 Weatherby in a pile of fractured parts, I thought it strange there was not one piece of bent metal in the pile.

F. Guffey

 

[fguffey]

RonAKA said: ↑

That primer that has the cratering does not look very flattened. I wonder if it is possible it that gun has excessive clearance between the bolt and the firing pin.
Click to expand...

+1 on this.. If you zoom in you can see how rough the primer looks after bolt face contact... What kind of primers are the silver ones...

Excessive clearance? If the clearance was between the bolt face and case head/primer the primer would back out unless; the case stretched between the case head and case body, after that we would be well on out way to having case head separation. And then there is the dent, the dent in the primer is large when struck, and then the primer conforms to the protruding firing pin. When a reloader has a bad firing pin spring the dent in the primers become smaller and then there are times the dent becomes an outie, some call the outie a pierced primer.

F. Guffey