Another Welcome and glad to see you made it to the Modern Muzzleloader site.
What you are experiencing is a crud ring in your barrel where the bullet seats on top of the charge. It is caused buy burnt powder sticking to the barrel. (REFEREED TO AS A CRUD RING) You need to be careful because the bullet needs to be seated on the powder charge. If not, you can get an excessive build up of pressure and destroy your gun and yourself. There should not be an air gap when shooting BP or BP substitutes. I had the same problem as you described with my Encore in 50 cal. But I got it all worked out. I still use 100 gr. of triple7 (two pellets), some 295 gr. power belts, and the only thing I changed is my ignition source. I am now using the 25ACP breech plug conversion. I am getting 1 to 1 1/2 inch groups with this set up at 100 yards. I has such good results, I switched my 45 cal Encore over to the 25ACP conversion. It has almost eliminated the crud ring in the barrel and clean up is easy.