Quote:
Originally Posted by WildBillG
For what it is worth Elkhunter11 is right different powders at the same pressure give different velocities. Salvee your equal resitance is the barrel not the powders pressure curve. When the big companies test loads it is with the same rifle for all the data per bullet weight. Some companies may change primers while gathering their data but very few.
I too thought it was a brass or case weakness problem with the 6.5x55 but I think it is a few weak rifles. Although I have an old Speer manual that has hotter loads in it for the military rifles than the newer Nosler manual has for modern rifles.
I like the 6.5x55 and wish I knew what pressure the modern rifles are to be loaded to. It should by all rights shoot faster than the 260 Rem and 6.5 CM but load data says no. If we look at that though the 270 Win is loaded to 65000 PSI and the 280 Rem only to 60000 PSI. Why they are loaded in the same kinds of rifles on the same case design.
|
The problem is the Craig Jorgensen Norwegian rifle which is also chambered for the 6.5x55, this rifle has a week action. On the other hand the swedish 96 mauser actions were all proofed at 66,000 psi, Many of these rifles were converted to 3006, 270 win 9.3x62 8x57 etc by swedish firms. I have one in the 270 Winchester, which is a 65,000 psi rifle. So bringing this rifle in 6.5x55 caliber to 60,000 psi is No big deal. The following picture shows the difference in pressure curves for slow burning vs. fast burning powders. Note both curves end at the same velocity. I uses slow burning powders to stay away from the high peak chamber pressures of the fast burning powders. This may be why published pressures show different velocities. Cup pressures are taken in or close to the chambers. Strain gauge measurements can be take anywhere along the barrel.
