Howdy Dai!
I shoot with GW and he's got a WEALTH of info locked up in his brain, and he's a patient teacher.
I learned this the hard way. I saw some 405 gr Meister bullets, lubed with SPG, on sale from Midway a couple years ago. I says to myself, "Jeff, (for indeed this is my name) you better jump on that deal. With the SPG lube they'll be PERFECT for long range BP shooting." I finally got to shoot some at a 100 yd range near home. I wasn't overly impressed, but at least they were all on the 8.5X11" paper. I've NEVER been a great precision shooter; I prefer combat type shooting. So, what the heck. I went to my first match and GW was running it. We started @ 200 yds, went to 300, then finished @ 400 yds. Basically, beyond 200 yds, I couldn't seem to hit the broad side of a LARGE barn! At 400 Yds I somehow managed to accidentally hit 2 of 20 shots. Something of an ego deflater!
Well GW was spotting for me, making helpful suggestions, and being all-around helpful to the newbie. I asked if I could shoot a box of 20 rounds that I'd loaded with the same bullet, only I used IMR 4198 instead of 2F Goex. He said "Sure." I hit 18 of 20! At 400 yds! I was shocked, to say the least! GW looked at me and asked "Are those bullets Hard-cast or soft lead?" "Hard-cast," I replied. "There's your main problem" says GW.
The moral to this story is: iffn yer gonna shoot BP, get some good, soft (no harder than 20-1) boolits. If you're going to shoot smokey-less powder, then hard lead will be just fine.