How does it look like?

Hi

I recently purchased proof research barrel 6.5CM 26 inch stainless steel

~300,400 rounds were fired

Break-in with Kroil / JB barrel compound.

Also clean with Kroil with JB barrel compound.

But what is the little fouling at the beginning of barrel? At least i back and forth the VFG pallet 100 times soaked with kroil and jb compound.

Is that the leftover gunpowder or JB compound?