Hot 44 spl. in a magnum revolver

[Kosh75287]

With regard to using Unique and it's so-called "dirty burn" tendencies, I have yet to use or see used a published load for it in ANY cartridge that could not be "cleaned up" somewhat, by:
1.) Increasing crimp.
2.) Increasing charge.
3.) Increasing projectile mass.

None of these changes need be drastic.
Increasing crimp by as little as 1/8 turn (on a standard 7/8" x 14 threaded press) has always helped a little, and sometimes, quite a bit. Its efficacy depended on how heavy the initial crimp was.
Increasing charge by as little as 0.1 grains (yes, it CAN be done, with Unique), especially near max charges OFTEN helps. In 38 years of reloading, only once have I seen clear signs of excessive pressure when increasing the charge weight by 0.1 - 0.2 gr.
Increasing bullet weight usually results in decreased volume in which the powder deflagrates, from a deeper seating of the heel of the projectile into the case, which increases pressures. Again, it's been rare that I've encountered frank signs of excessive pressures when the bullet weight is increased SLIGHTLY (think 240 gr. vs. 245gr. in .44 Spl. or 250 gr. vs. 255 gr. in .45 Colt).
During one work-up, it was noticed that one of two lots of bullets cast from the same mold shot discernably cleaner than the other. Weights of bullets from each lot were different by about 3.4%, so apparently inertia had something to do with it, also.

[Unclenick]

It's an issue of start pressure and handgun cases have small enough capacity that if you don't have enough crimp or if the bullet is seated too deeply, especially with a lubricated lead bullet, you sometimes get lower pressure (opposite of what QuickLOAD predicts) because the primer has started the bullet out of the case before the powder burn was well established. That means the powder peak pressure is lower because it's making its gas in a smaller volume than for a well-held bullet.

You can detect these on a chronograph, usually. The loads that are being started out of the case by the primer generally have lower average velocity and higher velocity SD than ones properly anchored.

Another thing that can happen with a low pressure load is longer bullet jump to the throat can also lower pressure by offering too little resistance to build pressure against as the bullet slips forward over the extra distance. This likely accounts for why a load would burn cleaner loaded in a magnum case than in a special case, assuming the same crimp groove is used in both.