Accuracy would most likely suffer.its not purely for accuracy, its for medium power levels and trajectory for the task. Accuracy at such levels is just the question i was posing.
1400-1500 MV in a rifle is fairly hot for a .38.
They tend to run more in the 1100-1300 range with standard 158 gr. bullets.
Accuracy tends to excel more in moderate velocity loads.
One reason why some think its better to push a heavier bullet at a slower velocity, rather than the other way around.
I don't think the free bore is going to make much difference here. It's not very much. Chances are good the bullet would likely not even notice it.