Noel:
Beater had a TC BigBore 58Cal carbine for sale arround the $400 mark. TC or Thompson Centre is a good name that makes quality stuff, and Beater is a top notch guy.
Trust me, you load that stout carbine with real black powder (ffg granulation), in that size (58 cal) it will make plenty of smoke. Further with the price of lead being what it is, this is plenty big, you can still get components off the shelf, and will spend more time shooting becuase of it.
Further, casting for Smoke poles is a little different than casting for smokless. You want you lead as pure as you can find it99+ is not to pure. WW while fun to make noise, will be to hard to obtureate properly, and the accuracy will more than likely end up being poor.
I have done and shot a lot of different smoke poles, and even competed for a year or two. If this is his first smoke pole, the learning curve will be very steep, and it more fun when one has success, and wants to shoot more.
I would strongly suggest getting a good book, (the one Written by Sam Faddala) the title escapes me right now, and read it cover to cover. I don't agree with all that Sam has to say, but regardless of what ones opinion is, he has alot of experince, alot of things to share, and cover many if not most of the possible BP disiplines. Then if you buddy still wants to proceed, get a single barrel. Make that smokepole spu smoke, learn what it takes to make it accurate, then, and only then move on to a sxs double.
Just my 2 cents from what I have learn in my short time shooting bp.
regards and all the best
AbH