Thread: Old reloading data

Greetings All,
This is likely a good time to relate, perhaps re relate, some excitement I inflicted on myself while working up a load for my T3 6.5. I had gathered up all the 6.5x55 data I could find and found it conflicting and some of it very light. John Barsness had recently published his article on The Rules. One of these is that possible velocity increases at 25% of case capacity. After about two pages of calculations I arrived at the conclusion that the 129 grain SST projectile should be able to be driven at around 2,850 fps at the same max pressures as the .260 Rem. A conservative target of 2800 fps was set. There was chronographed data using 45 grains of AR2209 that gave 2,700 fps with the 129 grain SST in my rifle. Stocks of AR2209 were running low so a new canister was purchased and a test load load of 46 grains was chronographed, expecting about 2,750 fps. The chronograph read 2,860 fps. Oops. Further testing showed that current AR2209 is considerably faster than my two previous lots that were manufactured prior to about 2002. These days I routinely chronograph each new lot of powder and thus far have not found significant differences.
The other thing that is often ignored is projectile construction. Recently 129 grain Long Range Accubonds and 129 grain Interlocks with the same powder charge in a 6.5-06. The Accubond LR projectiles produced 100 fps more velocity indicating significantly higher pressure. This explained some of the differences in data I had been pondering over.
Regards Grandpamac.