I have done some accuracy calculations with in-game mechanics,
perhaps they are usefull.
The normal rule set uses 2D6 for "calculating" the hit-probability of a weapon,
that is rolling 12 is the best, while 2 is the worst.
After playing Btech Tabletop for ages i will give a small
example for this kind of calculation.
But before doing so i will state the assumptions for the calculations:
1.Clan Omnimechs are equipped with targeting
computers (which gives a bonus of 1 for hit calculations)
2.Clan Omnimechs are equipped with large pulse lasers
(which give a bonus of 2 on hit calculations)
that have an in-game range of 20 fields (=600m)
3.Pilots are no n00bs, that is they have targeting base skill of 2 or less
4.Clan Omnimechs carry 2-4 heavy pulse lasers
(2 for light like Cougar mech,
3 for medium like Ryoken,
4 for heavy like Mad Cat)
5.Direct LoS
Reference for example:
http://www.sarna.net/btech/bt-board-tables-bmr.shtml
Example:
Base targeting skill of 2:
means rolling 2+ with 2D6 in order to hit with no further modifications
Firing at maximum range:
penalty of 4 makes 6+ to hit with 2D6
Mech was walking (~15m/s):
penalty of 1 makes 7+ to hit with 2D6
Target was moving with no more than 18m/s (6 fields in 10 sec):
penalty of 2 makes 9+ to hit
Target was moving with no more than 12m/s (4 fields in 10 sec):
penalty of 1 makes 8+ to hit
Target was moving with less than 6m/s (2 fields in 10 sec):
deduction of 0 makes 7+ to hit
Target is stationary:
Bonus of 4 makes 3+ to hit
I guess the best estimations for moving ground targets of WWI is 12m/s in combat situations.
Pulse laser + Targeting computer:
Bonus of 3 makes
1+ to hit stationary target
5+ to hit moving target
Rolling 5 or more on 2D6 gives a probability p of (missing: 1-1, 1-2, 2-1, 1-3, 3-1, 2-2) 30/36 or 83.3%
Firing weapons in Btech is an independent event,
since the dice are rolled for each waepon indepentently.
The event that not a single pulse laser hits is (1-p)^n
with n is the number of pulse lasers.
n=2: total miss probability is 0,027778 or 2.78%
n=3: total miss probability is 0,00463 or 0.46%
n=4: total miss probability is 0,000772 or 0.077%
This means, mechs will hit a moving target following the
above mentioned assumptions at 600m with at least 97%
Stationary targets are hit with 100% accuracy
Now you might want to add some more penalties so I am doing another example:
For rolling 8 or more gives a probability p of 15/36 or 41.6%:
n=2: total miss probability is 0,340278or 34%
n=3: total miss probability is 0,198495 or 19.8%
n=4: total miss probability is 0,115789or 11.6%
So heavy mechs with 4 pulse lasers should still hit their target with 88%
Since mechs with energy weapons need not fear ammo
depletion they should compensate their lack of accuracy with endurance.
Another thing is, that if you can hit targets with 4 pulse lasers
at 600m with 88% at least once it is highly unlikely that they
can hit targets at 700m not at all.