okay I may have misspoken on my first velocity.
41.5 grains H4895 yielded 2670 FPS in an IVI case
40.5 grains of H 4895 yielded 2570 FPS in an IVI case
39 grains H4895 yielded 2500 FPS in an IVI case These are closer to expectations, but still on the warm side compared to what I'd believe LC brass produces.
all these above were with a Hornady 168 BTHP match cci 250 (I'm trying to conserve my br2's and I do not have any 34) This may warm things up, but the Hornady service rifle data uses the WLR which is the "hottest" standard large rifle primer of which I'm aware.
39 grains of H4895 yielded 2410 FPS in LC match brass.
39.5 grains h4895 yielded 2525 FPS in LC match brass
according to Hornady number 10 manual 308 Winchester service rifle section. the 39 grains in an LC match case is pretty close to data but the other half a grain is making way too much difference I'm wondering if I miss wrote something in the 39.5 was supposed to be 40.5. Looking at the Hornady figures suggests your wondering idea looks like a reasonable explanation.
making a note to myself to double check that...
but there is a definite pattern of the ivi cases shooting extremely hot and I've done some research on last night and it seems to be a pattern reading about that case..
I'm going to shoot some more stuff I made last night to see what comes up..
okay I just now reloaded and reshot through a chronograph 40.5 grains of H 4895 to see if I wrote in error. 2624 is what I got from this that's running a bit over a hundred feet per second faster than Hornady list that Hornady also used Hornady cases so that would drop that a grain to 39.5 which I shot the other day at 2525 so that sounds right to me now.
the more stuff I shoot and the more I experiment with it's gun seems to be shooting a bit faster than publish data would reflect across the board..
an interesting note 40.5 of IMR 4895 which one would believe would be at least close to the velocity of H 4895 there's only shooting 2550 75 ft per second slower than the H version. but also interesting it would not cycle the action...
