I have found that a shorter barrel that is bored 3/4 inch works best for me. I mean short, where the guts come up to about an inch from end. You might want to bore a long practice barrel, then take it to the chop saw and start by cutting off 1/8 inch at a time, then trying it, then cutting more and so on, until you get the sound you are looking for...
It might work, it might not, but it's interesting to see what the barrel length does to the sound of the call..
Good luck!