Re: belt expansion as pressure indicator
I'm not to sure about this but here's something to consider. My 416 Weatherby factory loaded ammo measures .602" on the belt with calipers and once it's fired is .605" to .606", thats .003"-.004" greater, that's 3 thou, not 3 ten thou.
But fire a less than max load after that and dia. stays the same. A max load will sometimes produce .0005" more expansion. So I think they refer to after the initial fire form from my experiance.
I once loaded 400gn X bullets with RL22 at 120gr to get 2700 fps which is the max velocity listed but is 12 grains over maximum Barnes load. The velocity fell to 2500fps with 120.5 gr and bolt lift got a little sticky with belt expansion moving from .606" to .607" in one firing. dropped back to 120gr and no psi signs at all, even belts stayed the same. The next lot of powder was worked up from 105gr and found the exact reaction at 118gr and at 118.5 velocity fell again. I went to the XLC and found even better accuracy with 115gr at 2550fps.
Hope this helps some.
[ 01-14-2002: Message edited by: Brent ]