OK, with ALL cast slugs/bullets whatever I've tried this. Load your BEST stuff.....weigh powder....sort for the best bullets, no visible defects, weigh all bullets/slugs whatever. Also do the opposite with the slugs. Take the ones that have imperfections, rounded bases, voids. Load them and try them at 50-75 yards. Usually it's verrrrrry difficult to determine which load was best/worst unless you take it beyond 100. I've actually had BETTER groups (occasionally) from the imperfect slugs so go figure. I rarely weigh slugs now, there are other things that can improve accuracy (filling the bases with wax is the best from my personal limited tests) other than 20 grains more or less. Even placing a wax cardboard wad cut from a juice box can improve things depending on the load and slug. I use to shoot cast bullets from a 308 out to 500M so I did a lot of casting and sorting those bullets. When I took the imperfect bullets and shot them at 100 yards there was no way I could determine, from the target, that they were the bad ones. At 200 and beyond yes, out to 100, no. Best of luck.