Thread: Lower than expected velocities

Greetings,
Over the years I have noticed significant differences in load data for 6.5mm cartridges in particular the 6.5-06. This has become worse since Americans "discovered" the 6.5mm bore. The Continentals had been working with 6.5mm cartridges since the 1890's and had worked out how to deal with the long projectiles and fast powders. Most of these rifles had slightly or sometimes more loose groove dia. When A2 introduced the 6.5-06 as a factory cartridge they seem to have used much tighter groove barrel specs which push up both pressure and velocity. The data put out by Hodgdon for the 6.5x55 agrees pretty well with my results but the 6.5-06 I have been working with (put together in the 1990's) produces significantly less velocity than the data would suggest, much closer to vintage chronographed data from the 1980's. To me this seems likely to be the barrels.
Regards Grandpamac.