A plain base bullet will work very well, with no leading whatsoever, at speeds up to at least 1400 fps in temperatures which are too hot to have fun shooting, or in cooler weather, at considerably higher speeds, if you fit the bullet properly and if you use any one of the LBT bullet lubricants. Either the commercial which is a hard lube, or the blue, which is softer, or the Blue soft which is softest. Lube hardness has not one thing to do with controling leading. Lube quality is what does it. But barrel smoothness, and straightness, along with bullet hardness are also factors. For best results from you new contender, lap the barrel, using our LBT lap kit, ESPECIALLY of you want to use pb bullets. Gas checked bullets will forgive quite a bit of bore roughness, and allow trashy wax that some call bullet lube to work acceptably.
Please remember, guys, I'm a nasty customer when it comes to people jumping answers ahead of me, and delete most who do it. When a question is asked of me, on my forum, I'm to get the first answer. Comments after that are fine, as long as they don't contain old wives tales and folklore tricks on making lead work. Cast bullets are a mechinical thing and all information about making them work MUST be solid fact or I'll delete it. I've made an exception above but salted it down good with my answer on lube hardness.