Richard,
One more thing - I noticed on re-reading your original post, that the bore is "rough", which I imagine = pitting ( = corrosion in the past).
Pitting tends to cause problems if shooting non-jacketed soft metal bullets.
Here's a rough analogy: Imagine you were using a file to file a piece of lead metal: the file teeth would become clogged and the file would become "leaded". Quite soon the file would would be useless. So most of us only make this mistake once. Same applies to a grind-stone: never grind lead. But if you file or grind harder metals like copper, steel, etc. the metal dust falls away and the file or grind-stone does not clog. Same sort of thing occurs with a pitted bore and lead bullets, I fear: leading of the bore occurs, your accuracy falls off quickly, and you will spend a long time mining lead from the barrel to unclog it.
Rob