Furthermore, I think it depends on the range of the weapon, (i.e. the trajectory of the rounds fired) the range to the target and the range of the intervening units.
aza mentioned the cone of fire. For any support weapon, you would have the potential of hitting any units (whether enemy or friendly) intervening anywhere along the path of flight to the target (and potentially also beyond if you miss the target). So, intervening friendly troops are problem if you want a clear shot at the target. This is especially true at short to long range where intervening units will block the path of flight.
Thus, if friendlies are in a location that is before or after the apex of the trajectory of the bullets along that path of flight, they are in the danger space of the weapon. If this is the case, you had better not take the shot or reckon with some dead friendlies as a result of friendly fire!
Take the weapon's extreme range and assume that the apex of the bullets' trajectory will occur at 2/3rds of the weapon's range. That is the trajectory of the bullets (on a normal gravity planet) would reach their peak at that point.
At short to long ranges this is not important, because the trajectory of the bullets will be too flat to fire over anyone, but since MGs can be set up for a far ambush and you could even set up plunging fire over an intervening obstacle like a hill and theoretically also over other friendly units. However, keep in mind firing over friendly units with an MG is not a good idea unless you both have a well-prepared a position with aiming stakes and have tested it all beforehand. If you do this impromptu you run the risk of hitting your own guys especially if you are not 100% sure of their actual position. Your fire could also confuse them making them think that they are being fired on by your MMG team. Still, in battle it happens that people take these risks.
So in your second example if F4 fires at T-1 he is going to have to at least roll attacks vs. T-6. Depending on the situation T-4 & T-2 might get hit by accident as well. Here T-2 is in more danger than T-6. I'll explain further below.
The TL5 MMG has an extreme range of 120 (or 1200 meters), that means its bullets will reach their highest trajectory at 80 (or 800 meters). After that point, they will begin to lose height rapidly.
The way I handle this in my game is:
I determine whether or not the MMG team could conceivably miss the intervening units and give them a roll to try it with any applicable drms. Smoke, movement of the target or the intervening unit anything like that is a negative drm and will make the intervening unit more susceptible to getting hit.
If the MMG stand misses the roll it means they hit those intervening units. (Note: my players term these hits "incidentals" if they hit an enemy units and "friendly fire" if it is a friendly unit. I am so glad I never had to deploy with any of them btw.)
Bursts that hit an intervening units still travel on to the primary target, but are reduced in effectiveness by that number of hits scored on the intervening unit.
Thus, the bullets continue to fly on to the primary target where a second to hit roll is made. At long range you need a 10+ to hit but you get a +3 drm for the auto-fire bonus at long range. Let's just say that for the sake of argument the MMG team only fires one burst at T1 and the intervening units soak up 2 hits from that burst, I then have the MMG team roll to hit the intended target and reduce the number of hits scored by two. They need a 7+ to hit (10+ with a +3 drm). Lets say they roll a 10. That is 3 over what they needed to hit so the primary target takes 1 hit (3-2=1).
It is probably not the way that striker handles things, but it is more realistic and it works.
So using your example, if the MMG team fires off 8 bursts at T1, he has to roll 8 times to miss all 3 intervening targets T-6, T-4 & T-2, before rolling to hit the target! The chances of hitting T-4 and T-2 are somewhat reduced, because they are right around the apex of the bullets' trajectory at range 80 (800 meters). They are both 50 meters on either side of that apex and T2 is in more danger than T-4 because T-2 is in the segment of the danger space where the rounds are losing height fast. As the referee, I just make a couple of +/- drms here and have them roll what happens next.
I hope this all makes some sense?
