Having the bullets seated so there is a slight jump to the rifling is really a jacketed bullet technique and can work quite well.
For my 03, I seat the bullets deep enough into the case so they will feed thru the magazine. So, that means there is some jump. I normally shoot 20:1 in my 03 and I'm very pleased with the accuracy. I've won more than my fair share of matches with that rifle out to 500 yds. These are GC bullets.
I breach seat my .32-40 and as I posted in my .32-40 thread, with the properly sized bullet, which is tapered, I shot a 0.559 5 shot group at 100 yds. And my barrel is far from pristine being an original High Wall barrel that was freshened up to 0.326 and still shows pitting. I use 30:1 in that rifle. Bullets are plain base.