My 3 brass Uberti's measure .4295" and when I started shooting the first one, I ordered Desperado's soft bullets (8-9 BH) in .430" in 200 gr. and 240 gr. and experienced no problems.
http://cowboybullets.com/44-Caliber_c_10.htmlI didn't shoot a lot of them. Maybe 200. Much lower SD's using BP convinced me to quit playing with smokeless and I changed to the Accurate 43-230 C bullet for more lube. Those bullets will average 236.7 - .8 grains using 30:1.
The 200 Meter group below was shot with OE III BP and the Accurate bullets sized to .431". The load contained a .030 veg. wad. They will fit in my Uberti pistols, barely.
Billy
PS. I'm not so convinced that it is the bullet / bore relationship as it is a bullet / chamber relationship. These soft bullets bump up and squeeze down. I think you want enough bullet (width) so that the bullet has a better chance of entering the barrel straight. As Cholla says, "Bigger is better", but the gun needs to chamber the shells too.
I have never had a problem with leading.
In order to keep the cases straight (for minimum bullet run - out) I have tried every expander I can get my hands on and have had the best luck with Noe expanders set loose in a Lee powder die. The one I'm using is a .427 x .431" and after case spring-back, the ID is about .4285.
I've tried the case / bullet tension from O to .004" and they all seem to shoot real good until that 4th or 5th shot.