I have used them since they first came out. I have them in 45, 50 and 58 calibers. I'm going to buy a 54 soon since I picked a rifle in that caliber. I read an article in Guns & Ammo I think in the late 70's written by their BP editor Phil Spangenbaum(?). He said in testing them that for slow twist rifles go with the lighter weight offered. I have always gone with the lower weight even for 1in 48 twist rifles. I've never shot them in a fast twist rifle.I bought a 45 caliber 200 grain mold and have used it in my 45 CVA Kentucky rifle I built in 1980. And my CVA 45 Colonial pistol. It shoots great in both rifle and pistol and is very accurate. I shoot them a lot because you don't have to fool with a patch.To me the only downside is you have to make them. I'm not a fan of molding so I do at least 50 at a time. It helps if you have a very small scale like used on illegal pharmaceuticals. Any that not +/- a few grains go back in the pot. Good luck