To the OP, just let us know what barrel you are trying to add to your marker and we can let you know if there is an adapter out. Also what marker you have?
Originally Posted by Dyoel182
I thought the BT-4 had the course 98 thread. If not which BT gun am I thinking of?
Nope, it has a barrel adapter just like the a-5/x-7 with the same threading. They can also accept the A-5 Flatline.
I believe that might have been the bt-16 with the 98c threading, BT's first marker.