I imagin if you do the extra work to build such a horn it wouldn't be that much more to line the RB chamber with leather or something else to keep it quieter on a trek.
The whole concept sounds like more effort to use to me than more traditional ways to carry your RB's, and there's always the possibility the horns end cap could come off unexpectedly and dump out all the RB's.
How about a combo powder, patch, ball, fire kit, salt and smoke horn? Would only have to be about 2 feet long, but would need to come with instructions for use. :hmm: :wink: