I too am new to this and I too notice that with each successive shot it gets harder to seat a bullet. As you, I too use powerbelts and 777, except I use loose powder. I have shot 8 loads before it became near impossible to seat the projectile to the exact same depth. They went down the bore easy enough but the last half inch was hard, but not impossible. I had to put some muscle in it, but it went. When I clean the gun I notice a crud of sorts in the breech plug only. It obviously takes up more room each shot and that is why the bullet seats higher each time. Cayugad gives great advice and has more experience than me, so no need to reiterate his comments. I just wonder if there is a way to clean the breech area more thorough. With a cleaning jag you really can't scrub down there because you can't rotate the rod. Anyone have any advice on this, I 'd like to hear it.