Black gum will probably make a pretty good bow. I have never used it. One problem with it is it's very difficult to split. Interlocking fibers go everywhere inside that wood.
i just wanted you to know, i just remembeed i had tried makeing a monser bow, literally 9ft tall, out of a sapling, i just cut it to 80 inches and even though it has set from when i worked it and accidently left it strung for a week when it was green( i was just starting) it looks like it be be easily in the 120+ range
! it is only sapwood, and the rings are hard to distinguish, so just remove the bark and shape to your liking, when it dried it developed cracks in the belly so before bed im going to glue and clamp
if i were you i would try it if you can, it seems to have the potential of being a very good wood