You are indeed correct sir, about the barrel length. I had not thought about that aspect.

My gun has 25.875" barrels. So if you convert the so called "factory" ballistics (1900 fps in a 28"/30" barrel) to what can be expected from my shorter barrels, my loads are pretty close to the factory ballistics. Perhaps a load of 52gr of 4759 will push my velocity to just over 1800 fps. I'll have to give that some thought.

FWIW in my gun, 56gr of 4198 comes out at ~1600 fps. A chronograph comes in mighty handy for this work.