0,5-1 million shots?
Well, first of all it would be cone area. Hot gases destroy metal surface and cone area looks like pores and corrosion one.
Regarding chokes - yea, there will be some minor constriction changes, but first of all because of the same corrosion just before chokes, if we talk about carbon steel. You can clean barrels after every shot, but this corrosion will be there any way.
Thats why you need honing.

Geno.