I have no idea what a 84M barrel looks like, but the answer is almost certainly "Yes" ... especially since you said "BOSS type."
I built a 243 with a Rem700 bbl and a Turkish Mauser receiver, threading the end of the barrel with 5/8-24 threads. I then made myself a "BOSS like" tuner and threaded that to match the barrel. Sub MOA is not a challenge with this rifle ... even only using full turns of the tuner. I haven't gotten around to really trying to wring the last little bit out of the system.
If you are trying to use an off the shelf BOSS, or some other off the shelf BOSS type tuner, then it will depend on whether or not you have enough meat on your barrel to fit the threads of the tuner in question.
As for threading the barrel, I did mine before installation since I was acquiring pieces. I think that someone with a small enough spindle on their lathe or a long enough barrel could probably thread it on the action.
If you are going to make your own tuner, then I would recommend a trip to the USTPO (U.S. Trademark and Patent Office) web site. You will be able to find Browning's patent on the BOSS there and it will explain a lot of the relevant theory. I'd be happy to share what I know on this topic as well if you want.
Browning did some great engineering on this one ... John would have been proud. if they knew me, they'd be flattered, as I'm not very easily impressed.
Good luck,
Saands
