Over pressure ? Causes ?

[zzr1100]

My first outdoor range session of the year today ..
Using a club rifle (p14 in .308) using sellier and bellot fmj 147gr ammo.
Fired my 1st 10 rounds and while picking up the cases I noticed 3 had punctured primers and all had "witness" marks on the primer from the bolt face ..
A fellow club member said not to shoot that ammo through that rifle anymore ..
Now here is the question .. Is this over pressure .. What causes it ??
I've used privvi partizan with this rifle with no problem ..

[Dannywayoflife]

Too hot of a load for that particular action and chamber?

[StanDeasy]

Excessive headspace could cause this. If the rifle is OK with other makes of ammo, the S&B stuff could be a few thou short on headspace and/or have soft primer cups.

[Dangermouse]

Are you sure it is a .308?
Possibly a 7.62 that is not suitable with .308 ammunition,

DM

[The Gun Pimp]

Prvi Partisan ammo is quite softly loaded. Pressure in and old rifle can often be down to poor surface finish in the barrel - or a very dirty barrel. With brand-new brass, a slight head-space problem shouldn't be an issue - it will simply expand to fill the chamber - as it does when fireforming 'improved' cartridges.

[Chapuis]

Just out of interest did anyone check the nose of the firing pin for damage. It may not have been faulty ammo Sellior & Bellot is normally pretty good and I wouldn't say that their primers are particullarly soft either.

[zzr1100]

i taking the rifle back to the club tonight so hopefully may have some more insight into this later

[Maggot]

Another possible cause could be oil or moisture in the chamber/bore.

Wet ammo is unpleasant to fire and wrecks cases easilly.

Another possibility could be a dodgy batch of primers.

I have seen a CCI BR4 literally form itself round the end of the firing pin of my F/TR rifle.

It was at the lower range of a load test, the loads were very carefully checked, and it happened once, just once.

I still have it somewhere.

All of my rifles are stored with C2R oil in chamber and barrel, but then patched through with acetone or carb cleaner to remove it before firing.

Oil is best removed before use rather than during it with a bullet...ideally.

My guess is you may have had oil ONO in the chamber

[zzr1100]

I can understand oil in the bore or chamber being an issue with one or two rounds ... But with all ten ??
It was however chucking it down with rain yesterday ...

[Chapuis]

Maggot C2R is a cleaner and not an oil. Not that I would be keen on leaving either in my bore for any length of time.

Isn't it possible that the BR primer you mentioned was not at fault but that this was caused by under pressure loads rather than over pressure loads?