What aspect of a barrel's bore is the most important overall?  Is it the overall surface quality or the quality of the rifling?

I don't get out to go shoot as much as I would like, so most of my guns have bright shiney bores.  Several of them though are older guns I bought, and some I have built from kits.  

Today I was looking over a FAL that I built several years ago, and I noticed pitting in the last quarter of the bore.  The rifling is fine, but there is just random pitting due to it being a kit gun and having an older barrel.  Should I replace it?

What affect does slight pitting have on a bbl if the rifling is still healthy so to speak?  What do you all consider a good bbl?  Is it one that is shiney as a mirror, or just one that has strong rifling?  Or is it the throat of the bbl?

I am not talking about sub MOA quality here, just general health of a bbl in a military semi-auto rifle.

The two areas that are most critical to a rifle bore are the ends, the muzzle and the throat. The throat is just forward of the chamber. With each shot the throat is eroding. It will erode to the point that the jump to the lands is very great. As for accuracy, the muzzle is the most critical. If you have a worn muzzle, do not expect accuracy to be that great. I have seen fairly worn eroded throats still shoot fairly well due to a good tight muzzle. Where the bullet starts and where it ends are the critical areas.

By worn muzzle, do you mean the rifling up to the muzzle end of the bbl, or do you mean an overall wearing at the muzzle end?

In the FAL I was talking about, the rifling is still very strong at the muzzle, despite the slight pitting.  There are no nicks or dents on the bore portion of the crown.

Quoted: By worn muzzle, do you mean the rifling up to the muzzle end of the bbl, or do you mean an overall wearing at the muzzle end? In the FAL I was talking about, the rifling is still very strong at the muzzle, despite the slight pitting.  There are no nicks or dents on the bore portion of the crown.

It can affect accuracy.  We've had troubles with non-chromed M16 barrels in the Philippines that the muzzle corroded because soldiers always have their muzzles down (and inevitably touch the ground) for safety reasons.  Couple that with high humidity and the monsoon season.

When muzzles corrode at the end, the usual effect is that there would be flyers or the bullets won't group.