There are a ton of things that you would need to answers to be able to get directly to the problem... but basically I believe you have ran into the what has been named by another forum member as the T7 'crud ring'.

The 'crud ring' can be beat and/or nearly eliminated but it does takes some persistance. The easiest way to beat it is to switch to BH-209, it is a more expensive powder but if you do not shoot a lot it really can be the way to go.

Bore Butter is not normally the problem, depending on how you apply it, because Bore Butter is not a petroleum based product. From what I am reading here you might be using in between shots as a bore/bullet lubricant... that could lead to problems.

One of the biggest complaints in the world about T7 is that you have to run a patch after shooting... really doesn't bother me that much but to others it is a real pain. In the hunting situation it surely might be a problem, but normally with the right bore care I can shoot 4-6 shots without the 'crud ring' becoming a problem.

If you want to shoot T7 make yourself some regular Windex patches to patch the barrel with after each shot. Do not lube the sabot or the bore between shots... Here is a pictorial how to make the windex patches....



I believe a lot of the effect of the 'crud ring' is a reaction between what is in the T7 powder, the heat it creates, and the chemicals that might be in your bore. I would suggest not to use a petroleum based bore oil, or any oil with teflon in it. I believe it is a lot better to use a synthetic oil, such as Montana Xtreme Bore Condition, Slip 2000 bore oil, or Eazzox. Even the new form of BB, T17 on blue patches or Wonder Lube 1000 plus blue patches would be better that would be far better than bulk Bore Butter.

Just some thoughts as you are going to get a ton of different thoughts, so many it will be hard to work through them all.

Good luck...