Dude,You're in luck!
Your mention of using 4198 is the way to go! Been there, done that...a lot!
I have done plenty of experiementation on this subject.
Using 4198 is fine (very fine) as long as you don't mind the change in power...lower.
Otherwise the performance is excellent!
In either the 45 Colt case or the 454 you always Fill the case to mild compression...always.
I only size my cases down to where the heel of the bullet will be, leaving the rest of the case un-sized. This leaves a little more room for the powder.
Find your charge thus:
Using a fired but un-sized case, fill the case with powder to where the bullet will sit on the powder at the correct seating depth.
Weigh the resulting charge. Thats your powder charge.
If you're going to size the case just to where the bullet heel will be, add 0.1gr or 0.2 gr. of powder (so it'll be lightly compressed when the bullet is seated.)
If you size the whole case it won't hurt anything, you just have a little less powder/power to use.
Example: 230gr Gold Dot, lightly compressed-full case of 4198 gave 920 to 950 fps from a 5.5" revolver and gave 1400 fps [with very small variation] from a 20" carbine and very fine [surgical] accuracy for the 80 yds tested.
When tested with plain-base bullets up to 280gr it gave similar results.
Lots of un-burnt powder from the revolver but excellent performance otherwise.
The carbine was excellent in every way...just not up to "full power" potential.
Several deer have been unable to demonstrate any discrepencies in performance on their end of the experiment.
BTW, if you fire-lap your bore you'll get less lead in it...no matter what.
Beyond that, its mostly about bullet fit and lubricant as mentioned elsewhere.
Hope this helps.
