What BG to use for Tank?

I want to build a BG tank for decoy. What BG should I use?
I really would love somthing with High crit so attacking wont be a problem.

 

Cone horn III or the fishing event's bowgun. Both unavailable right now

 

I use diver's bowgun. I have cone horn III as well which is better but I can't be bothered to go and get a slot on it.
Sadly both of these bowguns are event only and are not available at the moment.
If you still want to build with bowgun I can suggest short musket. Its crit+ is not as high so you will need something like meikyo if you want to help prorating.
Decoy gives ampr regardless if you hit or miss so not a big problem with that.

 

I also use divers right now, it's in my profile pic xD, I also have corn horn 3 in my storage but i already slotted my divers and put seraph machina xtal on it for my 100% ailment resist tank so I dont have much incentive to switch to cone horn3, but like mayam said you still get the benefits of awesome ranged ampr even if the decoy's shot's missed and just using short musket, as well as massive single target aggro from the combos you can make from shot skill tree.