im not sure if thats the type of shotgun he's talking about?
when you reverse the spliff in your mouth and blow into someones elses, thats called a blowback here. lol
but what i think he means by a shotgun is the same concept as a bong except instead of the bowl...its just the pipe....you block the pipe with some tobacco and then put your weed....or more commonly here hash, ontop of the tobacco. if you can picture that?
then you cream up the chamber and when it all starts to slip down you "shoot" it and everything gets sucked into the water.
how to make on
http://www.totse.com/en/drugs/marijuana/161871.html
I dont think the size of the pipe will make too much of a difference...although obviously it will create more friction...so you may need to suck a little harder but i dont hthink iot would make tooooo much difference.