Currently we have a bunch of enemies hiding inside a big AM field. We don't want to melee them, being magic heavy party. We can summon monsters, like Bralani Azata's...
Summoned monsters blink out in an AM field, but a Bralani comes with a composite long bow (and arrows). Can a summoned Bralani shoot effectively at targets inside a AM field, or will it's arrows wink out of existence when they hit the field?
The equipment is summoned with the Bralani, so it will disappear in the AM field. Ask your GM, but probably, if you give the Bralani "real" arrows, the ones he fires will have no problem with the AM field.
Alchemist fire and acid should work, missile weapons, and so on. Even a wizard can use a crossbow, and your opponent's AC shouldn't that high, as they are in an AM field and most equipment and abilities don't work.
At worst you can wait till its duration ends.
Does your party have any arrows? You could just hand them to the Bralanis and avoid the question entirely.
If not, I'd say that the arrows would be ineffective. Summoned creatures wink out of existence when the summons ends and their gear goes with them. The creatures also wink out of existence (temporarily) while in an antimagic field. So their summoned gear would wink out in an antimagic field.
the way i rule (and i think it's supported by the rules) is that anything summoned is partly magical and on a timer. when the summon is gone everything goes back - poof. there is no real difference between the summoned creature's body and arrows that come along with it. it all goes when the summon is done (ether by the duration end or by taking enough damage) even spells the summon cast with a longer duration end when the summon end.
as such i rule that anything made by the summoning spell is considered a summoned creature or part of and wink out of existence along with it.
get them arrows from your backpack i guess?
EDIT: LOL, took me too long to post - two got it faster then me ;)
Have you considered using spells like true strike (+20 insight to next attack)? It should allow your wizard to have perfect aim with their crossbow for a single shot. If you have an empty spell slot to prepare the spell and a few pearls of power, you might be able to take out the spell caster before the fight begins.
The antimagic field is probably harsher on them than on you. You should still have access to healing magic and other utility spells, while they wouldn't. The effects would be even worse on the caster who has no option to walk outside the field (it follows them). Also, have you considered flying or teleporting past them? This might be a situation where its easier to avoid an encounter than it is to fight it.
I'm not sure if you can wait them out. If they went through the trouble to cast one antimagic field, then they might have more prepared. The minimum duration would be 11 (minimum wizard level) * 10 minutes, or 1 hour 50 minutes. Whether you want to wait that long to find out is up to you.