Unfortunately, Kenny is right in his estimation of the IAB. But it will do what your asking of it, hittin jugs at 200... but that's about all it will be good for. The weight of the first stage trigger is probably only adjustable VIA the springs. It will have to be pretty stout to do it's job.
If I could make a suggestion, a better "first buff gun" would be a Cabelas Rolling Block. The cost is under a thousand, and they are excellent guns fer the money. (I know yer gonna get flooded with replies about how great the American made Sharps are, but I know where yer comin from, that's a major amount of money fer a gun that doesn't see much shootin!)