Is the tank's MA one of the MGs, presumably the CMG? If not, you're done, you can't make a TH/TK roll with AFV MGs unless they are MA.
Presuming the CMG is the MA, it's a regular TH. Base 10 at 1-6 hexes, +1 for small target applies as well as moving for +2 so you're looking for a 7 best case. If you're buttoned it's another +1 for a 6.
If you're moving/motion I don't believe you can take an MG TH/TK shot since you'd be halved so I left out any bounding fire options. No crits for MGs so a 2 is just a hit. If you manage ROF, MGs are too small for acquisition so you'd be looking for another 6 or 7 on a subsequent shot.
So if you hit, then you roll the TK. MG TK base is 4, but is +1 at 2-6 hexes and +2 point blank. HT's armor is 1 so you're likely rolling for a 4 (4+1 - 1 AF). Make sure to consult the vehicle destruction table on rolling the number as MGs don't immobilize/shock, but stun instead.
'Course if you have a non-MG MA, which obviously most tanks do, you can't take the shot anyway. You could also just take a 6(+2) on the IFT, presuming the HT is CE, and hope to affect the crew.
Bret Hildebran
damavs@alltel.net
www.aslok.org