I have 2 of these. One blue and one stainless and they are both tapped for a scope. I have found pretty good success using 220 gr .456 bullets that are actually conicals for a Ruger BP revolver. Off rest, I can get 1-2 inch grps out of them @ 50 yds. I am probably just spitballing here, but my guess is that even with the bullet jump, the bullet is getting stabalized well enough as it is really biting the shallow rifling.
I also have the 45LC barrel and it is just as you said... a longer range cartridge out of that barrel. Either way, it's a fun cartidge.