I think what you heard is incorrect.

My experience with "Coated" bullets is that they produce less pressure with the same powder charge, so they lose velocity.

Thus, you can increase the powder charge, and should find that the pressure will be the same when the velocity regains the same, as compared to the previously loaded charge.

Pressure and velocity are directly related to one another within reason. The within reason has to do with burn rate of the powder and how long the bullet remains in the barrel, being accellerated to the target. As soon as the bullet leaves the barrel, velocity starts decreasing.

Note I do not have any experience with Barnes X to Barnes X triple shock. Hopefully this helps you.