Dude, you really need to do yourself a favor and read the stickies and search a little bit. Both of your questions would have easily been answered without posting a new topic...
But just because I'm not a prick, I'll make it easy on you- the threads are A5 threads (sometimes referred to as Carbine threads) they are the same as the tippmann a5 and x7. Any barrels that fit those guns will fit your BT4. In 10" there is the Opsgear fluted barrel, which is good quality and relatively inexpensive. 10" is on the short side, offhand the only other options I can think of are possibly the Special Ops Paintball C-series (not sure if its available in 10" or just 12" and higher) or a Palmers brass barrel which can get pricey.
Jay AKA Rogue...
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