Pappy,
I have tried several different bullets in the 45 Colt rifle to determine which is the most accurate.......especially at longer distances beyond 100m. In my experience I have found that bullets with the larger meplats (nose diameter) (Semi Wadcutters, Lee, etc) shoot larger groups at 100 than the traditional 45 Colt bullets (copies of the original 454190, etc) at velocities up to 1,200 f.p.s. At about 1,200-1,300 fps the larger meplat bullets shoot better groups. You might want to try a slower powder like Blue Dot or 2400 or 4227 and see if that helps.
That being said, a friend uses the same bullet wildman1 uses (Lee 255) over 6 grs of Trailboss for the 40m chickens, 50m pigs & 75m turkeys and 20/4227 for the 100m rams. The 20/4227 load seems to give him better accuracy at 100M than the 6/Trailboss otherwise he would use the Trailboss load there.
The 454190 is a good bullet but the meplat is a bit smaller than a primer so it would be a good idea to only load a few in the magazine at 1 time. To date, the very best groups I have gotten have been with the RBCS copy of the 454190. The RCBS bullet does have the same smaller meplat (nose diameter) though but has a disinct forward driving band whereas the 454190 does not. The Remington bulk bullet shoots almost as well.
Having had great success with the 427098 bullet in the 44-40, I decided to have Accurate Mold make a version of that for the 45 Colt. Previously, Fairshake had Accurate make an improved version of the 427098 (43-210B) with flat bottomed lube grooves which has worked extremely well. Thank you, Fairshake.
That Accurate bullet for the 45 Colt is 45-260B. As you can see in the pic it has a slightly larger meplat (not as large as the Semi Wadcutters and similar bullets) than the traditional (early) 45 Colt bullets so no issues with a magazine full.
I have only had a chance to test it once at 100 yards and it performed very well with a 10 shot group in the 3" range (5 in under 2"). Powder / charge was 9 / Herco. It's showing great promise....
w44wcf