on REVOLVERs and to a lesser extent auto loaders,each guns bore / throat size in relation to the bullet dia. the lube used, and the mold size, as cast versus sized, plus the alloy used effect the results, youll find that accuracy tends to be best when the bullets are .001-.002 over bore size and correctly lubed and loaded for minimal jump distance from case to bore lead distance.sizeing the bullets can detract or add accuracy depending on the relation between the guns prefered size of bullet to match the way the bullets enter the bore
if your mold cast undersize bullets sizeing them smaller tends to hurt accuracy, if your mold cast oversize bullets minimal sizeing tends to help accuracy