With some modification, the regular Gun Bearer will work on a J34. I had to run a 2" strap under the molly section on the belt and held it in place with two smaller 1" straps weaved through the molly's in the belt. With patience, you can get the upper strap attached to the sternum strap clip on the shoulder harness. It is not as tight as I would like it so, I decided to order the universal model for my F1 Mainframe. I will probably use it on my J34 as well.
I go back and forth between the Gun Bearer and Crooked Horn Gun Commander. Most of my day hunts with light pack, I usually use the Gun Commander. Hope this helps.