Interesting. I am trying to figure out why I have extreme pressure signs (e.g. blown out primers, flattened caseheads, blown out extractor) from a load that should be under maximum pressure. 4 out of 5 rounds showed no pressure signs whatsoever but one had the issues I described. The temperature outside was also 4 degrees Fahrenheit so it’s not like high temperatures caused it. I was shoot 6.5 Creedmoor with 140 grain Berger bullets and 42.5 grains of Winchester 6.5 Staball. I seating to further than the COAL in the reloading manual. So I have no idea why it happened. It is Lapua brass so the brass volume is pretty low compared to other brass. That’s the only explanation that makes any sense to me.
Really hard to say, and every firearm is different. If your whole gun is at 4* F, then it's possible the chamber was a touch tight and smaller due to contraction. If you loaded the cartridge long enough that the bullet was touching the lands, with no jump, that can also increase pressure. There are also occasionally powders that increase velocity slightly at lower temperatures, but I haven't seen any tests on StaBall 6.5 to know if it's one of them. Could also just be that particular combination with your particular rifle.
@@TechDregs It is weird. I gave it 20 thousandths of jump. It’s also a Tikka so it’s kind of designed with cold weather in mind. The velocity was also nothing crazy (2,711 fps). Yet, a primer blew, the casehead was totally mangled and when I was able to get the cartridge out, the extractor claw came falling out of the gun. Thankfully the extractor claw wasn’t damaged and I was able to install it back in place. I almost wonder if it could be due to condensation inside the barrel after firing multiple rounds.
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Interesting. I am trying to figure out why I have extreme pressure signs (e.g. blown out primers, flattened caseheads, blown out extractor) from a load that should be under maximum pressure. 4 out of 5 rounds showed no pressure signs whatsoever but one had the issues I described. The temperature outside was also 4 degrees Fahrenheit so it’s not like high temperatures caused it. I was shoot 6.5 Creedmoor with 140 grain Berger bullets and 42.5 grains of Winchester 6.5 Staball. I seating to further than the COAL in the reloading manual. So I have no idea why it happened. It is Lapua brass so the brass volume is pretty low compared to other brass. That’s the only explanation that makes any sense to me.
Really hard to say, and every firearm is different. If your whole gun is at 4* F, then it's possible the chamber was a touch tight and smaller due to contraction. If you loaded the cartridge long enough that the bullet was touching the lands, with no jump, that can also increase pressure. There are also occasionally powders that increase velocity slightly at lower temperatures, but I haven't seen any tests on StaBall 6.5 to know if it's one of them. Could also just be that particular combination with your particular rifle.
@@TechDregs It is weird. I gave it 20 thousandths of jump. It’s also a Tikka so it’s kind of designed with cold weather in mind. The velocity was also nothing crazy (2,711 fps). Yet, a primer blew, the casehead was totally mangled and when I was able to get the cartridge out, the extractor claw came falling out of the gun. Thankfully the extractor claw wasn’t damaged and I was able to install it back in place. I almost wonder if it could be due to condensation inside the barrel after firing multiple rounds.