Clarification about how magic arrows/bolts/bullets work?

Hi - I really should know this by now, but I've always been a little confused how magic arrows/bolts/bullets work and how they combine with magic bows. I'm also aware that original BG1 is a little different than BG2 in this respect, but let's assume BG2 mechanics for now, as I'm assuming this is what BGEE will use.

Firstly - AFAIK if you have, say, a +3 longbow, all the +3 does is add +3 THAC0, not damage, nor does it count as a +3 weapon for purposes of determining, for example, whether it can hit an enemy resistant to +2 weapons. Is that correct?

Okay, then assuming I have some +2 arrows that I wish to use with this bow, do they then add a *further* +2 to hit, giving +5 THAC0 overall from the bow+arrow combination, i.e. does the THAC0 stack?

Also does the +2 arrow add +2 to damage? Also AFAIK, the arrow *would* be able to damage enemies that are resistant to +1 weapons. Is this all correct?

How does things work with items that have automatic or magically created ammo? e.g.

Firetooth +4 (+2 fire dam., automatically fires +2 Fire Arrows)

Does this get +6 THACO overall? Can it be used with other bolts instead of the automatic fire bolts, if desired? Do you still get the +2 fire damage?


Short Bow of Gesen (+1-8 electrical damage, +4 THACO, no ammunition required, 20% elec. res.)

What does the ammo this fires count as, in terms of what it canh it, +4? Can it damage enemies resistant to +3 weapons? is it effectively firing +4 arrows (with +1-8 additional electrical damage) for all intents and purposes, including damage? Can it be used with other arrows instead of the automatic arrows, if desired? Do you still get the electrical damage?

Erinne Sling +4 (+4 THACO, creates 5 Bullets +4 once/day)

Does this get +8 THACO overall if used with the ammo it can create?


Any ideas? Thanks!