Yep, but in the .243 the pressure variation apparently doesn't occur with bullets under about 100 grains.
One problem with both rounds (again, info from pressure labs) is the short neck and shoulder angle. The combination results in relatively quick throat erosion, which in its early stages can also result in erratic pressure. Once the erosion extends farther down the barrel, pressures tend to decrease.
Thanks for the response. Wonder why you don't see the same thing in a 300 Win Mag despite a short neck and similar shoulder angle?
