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Old 09-01-2017, 06:50 AM   #7
mlangsdorf
 
Join Date: Aug 2004
Location: Austin, TX
Default Re: Battletech/Mechwarrior mechs in GURPS

I've run a Mecha game in GURPS 4e - using 5m tall Heavy Gear style mecha, not 12m tall Battletech style mecha, but I think the principles are pretty much the same.

My house rules from that campaign are below. You might want to adjust the scale: I was using MapTools to run the game online, so having 300 hexes on map was no big deal. Most of the rules are just clarifications on the existing rules for vehicle combat in GURPS Basic chapters 12, 13, and 17.

Terrain
'Mech scale combat occurs on maps using 5 yard hexes at rates of 1 second per action.

Trees are concealment, not cover, especially against large weapons. Every 5 yard hex of forest imposes a -2 penalty on attack rolls. This penalty is halved against SM+0 targets or the legs of SM+2 or more targets (since you're not firing through as much of the branches). Modifiers are cumulative.

Movement
'Mech scale combat occurs on maps using 5 yard hexes at rates of 1 second per action.

For simplicity, any large vehicle or giant that is moving on its legs is treated as a very large SM+0 character: they can accelerate to their maximum Move in a single action, or decelerate from their maximum Move to a dead stop just by not moving forward any more. They can also make tight turns, turning up to 180 degrees as part of a step or paying 5 MP per hexside change as part of a move action. They can move into any of their front 3 hexes, and turn to face the right and left front hexes as they enter them for free.

It costs 10 MP to enter a 5 yard hex of forest.

Control Rolls
A control roll is made against Driving (Mech) + Mech Handling - (Current Move MPs/10).

Failing a control roll in a turn causes a skid, so the 'Mech turns the way it intended but spends half of its current Move MPs moving in the old direction. Otherwise, failing a control causes the 'mech to randomly move 5 yards to the left or right or other movement as appropriate. Failing a control roll by more than the 'mech's stability rating also causes it to fall down down (and crash if it was moving at any speed, taking damage as though it collided with the earth).

Attacking
'Mechs have stabilized weapons and can Move and Aim. They still lose their Aim bonus if they make a defense roll, fail a control roll, or get hit by an attack that either does damage or knockback.

Attack and Piloting rolls during a Move and Attack maneuver are at -2 if the 'mech moves in anything other than a completely straight line or has to make any Control rolls. There is no penalty to attack or Control rolls made during an All Out Attack maneuver.
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