No I have never seen that.I have a 45 and a 50 cal encore,the 50 cal has had at least 500 shots through it in the last 3 years and the 45 probably has somewhere near a 1000 shots in the last 2 years.Still haven' t found a decent load for the 45 but the 50 has allways shot good.
But I do agree that after shooting it some that it smoothes the barrel out ,if it has any burrs in it.In all my guns I use the JB' s to do that before shooting them the first time.
Sure wish my 45 would clover leaf after 200 shots,one thing about shooting the muzzleloader it is fun to shoot but it does get pretty expensive if you shoot alot.This week I shot the encore 50 cal 25 shots and a savage 140 shots and a knight 10 shots,$$$$