Okay, this may be a really dumb question but I'll ask anyway. I've gotten my first over/under shotgun and it has a barrel selector switch to let you choose which barrel shoots first. Are there any good arguments for choosing one over the other as the first one to shoot?
Thanks!

You shoot the one with the choke that is appropriate to the situation. Most people, in most situations, choose the more open choke (all this is assuming you have different chokes in the barrels, of course)first. However, in some situations, for instance, with fast incoming birds, it is better to shoot the tighter barrel first and then use the more open choke as the birds are getting closer.

In general most competition shooters choose to shoot the lower barrel first.

The theory is less recoil "pitch-up" and therefore faster recovery for the second shot.

Shooting the lower barrel first theoretically gives you less muzzle rise, thus allowing you to recover more quickly from the recoil for the second shot. In practice, I've never been able to tell any difference in muzzle rise between the two barrels.

I agree with Gato for hunting. If you are hunting ground-dwelling birds you normally expect them to flush away from you, so your first shot should be with the more open (usually under) barrel and second shot with more choked upper barrel. If shooting something like incoming doves, then you might want to reverse that sequence.

After shooting your new O/U for a while, you'll get used to using the barrel selector and will instinctively choose the more appropriate choke as circumstances change. I know that I've had the experience in dove hunting of having the "U" barrel selected in anticipating the nearer, then further target coming from behind only to have a pair come from far across the field straght toward me. I simply thumb the selector to "O" in anticipation of shooting the first bird further away followed by the second one closer (usually wishful thinking, I might add as the second shot is typically spent on the first bird which the first shot missed ).

Thanks for the info. Hadn't thought about possible reduced muzzle rise or the idea of changing with incoming birds to match the chokes...good advice to try on the upcoming dove season!!!!

I guess I'm getting old, I thought the question was about choke selection but it is normal, as the above posters have pointed out to have the more open choke in the bottom barrel. HOWEVER, and I don't do this, but I have a friend who is a very good shot that reverses the process WHILE HUNTING (as opposed to target shooting) and hunts that way all the time. Why, because when a third shot presents itself with an O/U.....which is surprisingly common......it is MUCH faster to load the top barrel with one extra shell and fire it. If you shoot the bottom barrel first, not only do you have to load the gun, but you have to switch the selector or pull the trigger twice if the gun is not recoil set. Both take too long and detract from what you should be doing which is trying to kill the bird.

Very helpful thread to me. Thanks all.

Same reason to shoot a side x side "inside" barrel first. Recoil is more inline with the shooter.