Since I've Never Fired a Double or O/U Shotgun...
 

How quickly can one switch from one barrel to the next one, assuming you don't have a double trigger?

o/u or s/s shotgun
 

instantly on my o/u 12g. ( one trigger). usually no flicking a barrel switch is required.

It might be a few milisec but I never notice the lag..

A very long time ago, one of my friends had an O/U double barrel and the trigger was two-stage. The first stage required slightly less pressure than the second stage but I seem to recall that if you squeezed quick & hard, you'd fire the second barrel almost the second after the first barrel had fired.

That's exactly what I assumed HQ was describing.

So does the right or left barrel fire first? (Or upper/lower?)

I'm beginning to think that the T2K rule about being unable to fire both barrels at once is more a game mechanic than IRL.

Well, mechanically you can't fire both barrels at once but with the two-stage trigger you can fire the second shot so quickly that for game purposes it could count as both barrels fired at once.

O/U or S/S 12 gage
 

Yes I my intention as Targan writes- but to word it differently:

one trigger double barrel sg:

the second barrel can be fired as quickly as you can let out the trigger and pull it again - maybe a 10th of a second or maybe faster for some shooters.

In RL you can go ba-bam and have two shots of in the space of less than a second - but I would argue that the second shot is influenced by the recoil of the first etc.

Two trigger shotgun - I think you could get both of so fast that they could be countd as one roll game - wise. Gunsmith customization might also be done to this effect.

As for which barrel fires first ( upper /lower / right/left) I believe the international standard is the one with the least choke first trigger/first barrel and the one with the most choke second. Despite having fired of one and reloaded one barrel a thousand times I cant for the life of me remember if the top i sfirst or the bottom. I think top is first.

I used to own a double barrel 12 ga. It was a side by side. Two trigger system. Left was front trigger, right was rear. I NEVER tried to fire any where near together. I am a pretty big guy, but I always fired one, re-acquired target, fired again.

My $0.02

Mike