I had a local gunsmith convert my Ruger Blackhawk 45 Colt to an oversize line reamed 5 shot cylinder with a new 4 3/4" barrel in the same caliber. I am so excited about how well it shoots, I thought I would share some of the results. The first group I shot was at 50 yards with a GC 340 grain Lyman over 22.5 grains of H110. 5 shots were at 2 5/8". The 2nd group I shot through this revolver was a GC 325 grain Mountain Mold bullet with a big 80% meplat. 5 shots were at 1 1/2" at 50 yards! I hope I attached the picture properly. I shot these same loads at 100 yards and the Lyman shot a 5 shot 4 1/2" group and the Mountain Mold bullet shot a 6" 5 shot group. 4 of these shots were 4 1/4". Both of these loads chronograph right at 1200 fps. It amazes me to be able to shoot groups that tight with open sights and a 4 3/4" barrel! It would be interesting to see how good this thing would shoot with some optics, but this is a packing gun and it shoots good enough for me.
PB 255 grain bullets at 1200 FPS shot 3" at 50 yards. The heavier bullets always shot better in the unmodified Blackhawk. Even with proper allignment a long bearing surface seems to shoot the best.
The cylinder throats are .4515 and the groove dia is .451 and the bullets were sized to .452. After 50 rounds there was absolutely no leading in the new barrel. There was always a dark area on one side of the barrel and I tried laying the pistol on the other side after firing and the dark area moved to the other side of the barrel, so I'm sure it is smoke settling. There was very slight leading after shooting 50 PB bullets, but a couple shots of GC bullets would remove the small streaks of lead.
I couldn't shoot groops this tight at half the distance with the same unmodified Ruger Blackhawk and there was always lead in the barrel after a few rounds. It seems that proper sizing and allignment solved all of my problems. I should have modified this pistol long ago. It would have saved me countless hours of trying every load, bullet size, bullet lube, etc availiable.