M96 rupturing primers

[Schnitzelmahn]

hello,

took my new Swedish m96 rifle out for the first time the other day, and fired a box of S&B 6.5x55SE 140gr FMJ. Virtually all the primers on the brass were set back after firing (they were all set in originally). 3 primers were completely pierced, but no sign of any gas blow-back. Wondering if this is a known issue with the S&B, or if there might be a firing pin protrusion or headspace issue (if so, how can i check?). Perhaps its an issue related to the cold, since I was firing outdoors in -30C weather.

thank

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[browningautorifle]

Sounds like a high pressure problem. Is the ammo new or surplus? What was the source? Factory ammo can change when stored badly too...giving hi pressures and pierced, setback primers.

[RT1shot]

The only way to find if it is a head space problem is to get a NO GO gauge and give it a try. If the bolt closes or almost closes on it you have a head space problem. I would get another brand of ammo and give it a try first.

[Schnitzelmahn]

the brand is Sellier and Bellot from tradeex

[cipherk98]

Was the gun fresh out of the crate and greasy or just new to you? If the former, did you clean all the cosmoline out of the bore, chamber, and action? Any pictures of the spent brass?

[browningautorifle]

I would get another brand of ammo and give it a try first.

Agreed, and get a store bought box not Tradex. Get something good.

[mtoms]

If it is a pressure issue, it is more likely low rather than high. Insufficient pressure can allow the case to move back in the chamber to the point the firing pin pierces the primer. The case should expand and adhere to the chamber wall at the instant of ignition and stretch to fill the gap lengthwise-preventing primer setback.

Of course if you combine low pressure with a little excessive headspace this would make the issue worse.

Also some manufacturers of 6.5x55 use brass stock meant for 30-06 class -cartridges undersized at the head - which requires more expansion at ignition. I don't know if S&B is one of these.

Regardless - I would try another brand and see if the issue goes away - preferably European - I know Norma brass is correct - I've used it. Maybe Privi is as well.

Headspace check would be prudent but I would use a field and be looking for excessive headspace-the fact you can chamber rounds indicates it is likely not insufficient headspace.

Regards
Marty

[browningautorifle]

The only way to find out about pressure is with the proper equipment...unfortunately scarce... Low equates to high though, you can still damage things. Were the primers flattened or just set back? I'd expect flat. I agree about using Norma...for sure. Just 20 rds of real nice ammo should tell.

[Buntlineguy]

I have had bad luck every time I used S&B ammo. Head separation with .303 and failure to cycle in semi-auto pistols in 9mm and .380. Out of 50 .380 rounds only 2 cycled the action. No problems with any other brand. I will never buy another box of S&B.
B

[CINDERS]

S & B 303 brass never lasted more than 2 reloads sometimes just one in my rifles , the H/S on my 303's snug nicely at .067. I have .064 but do not use it. My R.P brass some of it is up to 12 reloads and going strong I just annealed a batch as I fls all my brass for them as reloading for 5 different 303 rifles it is easier to just FLS. Allot of my friends have had same results with S&B.
I would have thought in the miliseconds on detonation of the main charge (Not the primer as it initially backs out when detonated) that the case would grip equally in all directions! As #3 suggests I would try a different brand of ammo and see if that has the same result then you have a bit better understanding (hopefully) as if it does not do it the ammo could be the issue if it does the same to another brand then it is the rifle. The F.P protrusion needs to be checked also the radius of the firing pin head that strikes the primer it may be to sharp!

If you had left the ammo out in the car overnight ready for a quick scoot in the morning the metal may have been brittle due to minus 30 degree temps may have caused issues I am no metalurgist others may have had experience at -30 degree temps with ammo. Jim does it get that cold up in Canada!

On a shooting course I attended we had hot/cold ammo velocity tests the ammo I fired had been heated to 50 degrees C in my 6.5 x 284 they were hot reloads before the heat up the primers backed way out with some gas escape I only fired 2 rounds both the same result and called it quits for doing that as the SAAMI of 60,000psi limit for that round would have been surpassed I reckon
The Mag chrony clocked the 140 Berger's doing 3,070FPS & 3,064FPS according to my records had a good E.S I suppose 6fps .