CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
T. O'Heir beat me to my question. Is it actually something coming back leaking through the slide and frame gaps and speckling your face and glasses, or are you just referring to the muzzle blast? If it's the former, the stout load may be running your gun a bit hard and a stiffer recoil spring may help. If it's muzzle blast, it's no wonder. Hodgdon has a measured 1044 fps for their maximum load, while QuickLOAD predicts 1042 fps, suggesting its powder model is pretty close, though its peak pressure is a little higher. It suggests only 85% of the powder is burning inside a 5" test barrel, and it will be still less in a shorter barrel. So this stuff is running high muzzle pressures and temperature, both of which make for a lot of muzzle blast.
You can get more complete burn and similar velocity from N340, but it's harder to find. It should burn more completely (92%) for you.
.45 Auto can be a funny duck. Faster powders also appear to have a stab at it as long as you are willing to load to +P levels. These will cut muzzle blast significantly. Since the loads needed exceed published maximums, you will have to work up to them carefully.
The suggestions to try HP-38/231 is good. Same with Bullseye and Unique. You need a chronograph and an eye for pressure signs to do this, but you'd be surprized how fast you can get a bullet moving with them.