Will elevation affect pressure

[Beluebow]

As mentioned, a change of altitude (atmospheric pressure)... is no causative factor for higher cartridge pressure.

Look elsewhere for your source of elevated pressure.

+1

 

[Idaho Lefty]

As mentioned, a change of altitude (atmospheric pressure)... is no causative factor for higher cartridge pressure.

Look elsewhere for your source of elevated pressure.

How many grains of, StaBall were you using ?
StaBall HAS, a "Burn Rate" like 4350 and could be, pressuring up with, those 195's !
Hogdon calls for,.. 66.3 gr's with, 190's and 65 grs with, 200 grainers.

 

[Jpron]

How many grains of, StaBall were you using ?
StaBall HAS, a "Burn Rate" like 4350 and could be, pressuring up with, those 195's !
Hogdon calls for,.. 66.3 gr's with, 190's and 65 grs with, 200 grainers.

I'd have to go back and find my data but I wanna say low 60's

 

[Jpron]

The wet case theory is interesting, that round that jammed my gun was in my pocket and I was sweating heavily that day. We hiked about 4 miles in some pretty deep snow.

 

[parshal]

I bet you're running a fairly warm load. Water on cases or in the chamber can dramatically increase pressure. I 'discovered' this during an NRL race gun match when it was pouring rain. My zero pressure 6BR load started having bolt lift issues. I'd bet 20% or more of the competitors had issues with some being unable to run through a ten round stage without locking their bolt.

 

[Pdvdh]

Wetted cartridge exterior does not increase chamber pressure.
It can increase bolt thrust, as the friction between the chamber wall and cartridge exterior is reduced. Allowing the casing to exert a greater force against the bolt face.

 

[parshal]

Sure, that may be the true reason. But the end result is a sticky/stuck bolt and reducing the load eliminates it. At least in my experience.

 

[Idaho Lefty]

I've done, several Late Season, Snow / Rain and very Cold, Hunts, in Idaho, Wyo and Northern Arizona. I keep My .270 WSM ammo, in a spare Tikka Magazine, in a plastic Sandwich Bag ( in Coat Pocket ) to AVOID ammo getting Wet and I always Hunt with, a Dirty "Fouled" Bore covered with, Elect Tape over Muzzle. Any Cleaning ( Like JB's Paste ) Oil or, grease Residue in Bore and Chamber ( Except, normal Powder and Copper Fouling ) CAN,.. Raise those, chamber Pressures !
I work-up my Loads, in the winter / early Spring and Re-Test them again, in the August Heat for safety. I've noticed My Accuracy comes in BEST at, 1/2 to a full Grain Under, tip Top, Max Loads, usually.