Gear has basically covered the paper ring. That is exactly what I was referring to. What I have concluded is that if the patched boolit has nose resistance entering the bore, the boolit base will tend to bump up. I have experimented with reducing the nose section diameter and also shortening the boolit so as to allow the boolit to start moving before encountering the resistance. This nose resistance is I think, also responsible for boolit canting in the bore.
My little carbine with its really worn and eroded bore, especially the throat area, shot well with a softer alloy with a two-diameter sizing of the boolit core. Unfortunately, I don't remember exactly what I was doing at the time and my notes are unclear. It won't be too difficult to figure it out since I still have some of the same boolits left, including patched ones and photos so I can see what paper I was using. It may take me a little time to figure all this out due to circumstances. I do remember that the boolit in question was a 208gr round nose with a small hollow point. I have a photo of a fired one using a light charge. The curious thing is that the patch stayed on right into the catch medium.
Then the bore rusted and that didn't happen anymore. But now after some polishing and firing, it is smooth again.
I'm compelled to post a picture of it. It's a great little rifle! Fun to shoot.
Anyway, Initially, I developed a load for it by stepping up the powder charge until the patch was fully coming off at the muzzle. But only just.
After a while, the accuracy dropped off and I found that the bore had polished up and was no longer cutting the patch through, so I had to increase the powder charge.