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Battletech to GURPS Conversion Notes, V2.0
by Brandon Cope (firstname.lastname@example.org)
August 7, 1999
BattleTech is a trademark of FASA, Inc. GURPS is a trademark of Steve Jackson Games Incorporated. All GURPS books listed below are copyright and/or trademarks of Steve Jackson Games Incorporated. Combat Option #1 is based on a Roleplayer article copyright 1990 by Steve Jackson Games Incorporated.
The rest is copyright 1999 by Brandon Cope
This is a major revision to a set of Battletech to GURPS rules I first wrote in '92 or '92. When I noticed them mentioned in a GURPS FAQ, I realized that they badly needed to be reworked. A great deal of the rules have been expanded or changed (the biggest was changing the abstract combat option to use GURPS Compendium II rules rather than the long-out-of-print GURPS Humanx).
These rules assume the GM is familiar with both GURPS and BattleTech. I'll be the first to admit that these rules are a bit choppy and somewhat unorganized, but I'm currently busy with a novel, short stories and (paying) roleplaying articles. Also, I haven't played BattleTech in a while, so I'm a bit rusty with some of its rules.
Roleplayer #19 has a GURPStech article by Rich Ostorero (the origin of the term 'GURPStech,' I believe).
Brief Note: When I started playing BT, there was no such thing as ferro-fibrous armor, omnimechs or other technology of the Clan vs Inner Sphere struggle (I don't even think there was a Clan/Inner Sphere struggle in those days). Therefore, only the basics of BattleTech (plus vehicles) are covered below. My BT source is the outdated BattleTech Manual: Rules of Warfare (1987).
Note: If you run out and buy GURPS Vehicles and GURPS Mecha, you probably won't need much (if any) of what follows. These rules assume that you won't be designing mechs with those two books. But feel free to.
- BT: Battletech
- p.CIIxx: Page reference to GURPS Compendium II, page xx
- p.Bxx: Page reference to GURPS Basic Set, 3rd Ed Revised, page xx
While the conversion list for the 'Mech may seem long, note that it covers all combat options (see below under Combat). For example, if Combat Option #4 is used, only Firepower Rating and Defense Factor are relevant.
- Cruising Speed: BT walk speed times 6 (in mph)
Option: Not all 'Mechs (or vehicles) are equal. Add 2d6-7 to Cruising Speed (from -5 to +5 mph). Performance can be tweaked just like starship engines (p.S35) using Mechanic ('Mech) skill.
- Maximum Speed: cruising speed times 1.5
- Jump Distance: 30 yards per jump number
- Passive Defense: 1 point per 2.5% of mass devoted to armor (maximum PD 8)
- Damage Resistance: BT armor value times 100
- Internal Component DR: 20-50
- Internal Component HT: tonnage * 300 (x0.5 for gyroscope and fusion plant, x0.1 for cockpit)
- Dodge: one half of Driving ('Mech) (but no greater than BT cruising speed)
- Firepower Rating (FR): maximum BT damage the 'Mech can deal in one BattleTech round (assume every missile in a volley hits). If the heat generated is greater than the number of heatsinks, subtract the difference from the Firepower Rating. Do not count physical attacks (punching, etc.).
- Defense Factor (DF): (PD+Dodge)/4, minus 1 (minimum 0.1)
- Weapon Ranges:
- 1/2 Damage: upper medium times 100
- Maximum: upper long times 300
- Option: Double 1/2 Damage range for tracked, wheeled and naval units, as they are a more stable firing platform than a 'mech, VTOL or hovercraft.
- Weapon Accuracy:
All 'Mechs and vehicles come with a Fire Control Computer. Divide the target's range/speed (before finding the modifer) by the FCC rating (eg, /2). For simplicity, assume all 'mechs and vehicles have a /4 primary system and a /2 backup system.
- 8-12 for MG and ACs
- 15-20 for lasers/PPC
- 6-8 for LRM and flamers
- 4-6 SRM
- Weapon ROF: (suggested)
- MG: 8-20
- AC: 1-8
- Lasers: 4-12
- PPC/Flamer: 1
- LRM/SRM: as in BT
- Weapon Damage: 6d x (20 x BT damage), halved for ACs
Note #1: For some weapons (especially the MG), this is really a simplification of automatic fire rules. If the damage of an individual round is desired, divide the total damage by the weapon's ROF (GM's decision) and increase the result by 20%. Heat is generated per full ROF burst, not per individual round.
Note #2: For simplicity, use BT damage and armor values when 'Mechs are slugging it out, and convert to GURPS damage as needed (eg, pilot injury).
Note #3: Like other non-living objects, impailing and cutting weapons get no bonus against 'Mechs or vehicles. Also, bullet and beam weapons (anything but missiles and bombs) do only 1/10 damage to internal components. Missiles and bombs do normal damage. (This may seem generous, but, for example, an AC/5 with ROF 4 does 400 points of damage (per shell) on an average hit.) Missiles are assumed to be shaped charge; ACs and MGs use APFSDS (or some alphabetic derivative) which gives a (3) armor divisor.
- Troop Strength (TS): For a really simple system, use the mass combat rules in Compendium II. A very rough estimation of 'mech TS would be (tonnage/2).
GURPS Vehicles use the same rules, except as follows:
- Top Armor (turret present): DR = front armor
- Top Armor (no turret): DR = side armor
- Underside Armor: DR = rear armor
- PD is halved.
- Dodge is halved for hovercraft and quartered for tracked/wheeled and naval units.
Sample 'Mech Conversion
(This uses the ubiquitous Merlin from the Rules of War construction example.)
Merlin, 60 tons
- Cruising/Max Speed: 24/36 mph (the optional speed modifier was not used)
- Jump Distance: 120 yards
- PD: 6 (10 tons/ 60 tons = 16%, 16/2.5 = 6)
- DR: ? (armor wasn't allocated in the rulebook, but front torso DR is probably in the 3000-3500 range)
- Dodge: 6 (assumes a Driving skill of 12+)
- HT values:
- Internal Structure: 1800
- Cockpit: 900
- Jump Jets (4): 300 (each)
- Weapons: varies
- Fusion Plant: 3450
- Gyroscope: 900
- Heat Sinks (9): 300 (each)
- FR: 26 (+29 for weapons, -3 for excess heat)
- DF: 2
- TS: 30
|Med Lasers (2)
||2000 (200 bursts)
||120 (24 salvos)
NOTE: Yes, you could convert the mechs (or design new ones from scratch) using GURPS Vehicles and GURPS Mecha. However, such a move may turn off BattleTech veterans. Also, it takes more than a few minutes to crank out new designs with GURPS Vehicles/Mecha...
- Driving ('Mech):
- As per normal driving, but uses the same high IQ bonus as Guns. LAMs also require Piloting (LAM).
- Tactics ('Mech):
- Required if the character expects to survive for long; see Battle skill below. Defaults to normal Tactics at -2.
- There is no 'battlemech' specialization; use Land.
- GURPStech specializations are machine guns, autocannons, lasers, missiles, PPCs and flamers.
- Shortsword ('Mech):
- This applies to any balanced melee weapon used by the 'Mech. It defaults to Shortsword-3.
- Axe/Mace ('Mech):
- This applies to any unbalanced melee weapon used by the 'Mech. It defaults to Axe/Mace-3.
- Battle Skill:
- This is an overall evaluation of a 'Mech pilot's combat effectiveness. It is the average of Driving (Mech), Tactics (Mech) and applicable weapon skills. Since most 'Mechs require 2-4 Gunner specialities, determining Battle skill for GURPStech can get a little complicated. There are several solutions for determining the pilot's effective Gunner skill (for purposes of calculating Battle skill only):
- straight average of all Gunner skills applicable to the 'Mech
- the pilot's best Gunnery skill applicable to the 'Mech
- a weighted average based on the number of each weapon type (my preference, but I was a math major...)
- a weighted average based on weapon tonnage
- a weighted average based on weapon (critical) spaces
Whenever a mechwarrior would take damage under BT rules (high heat, head hit, etc) apply 1d6 damage (and 1d6-3 fatigue if the cause is heat) per point of BT damage (this does *not* apply to wounds from weapon fire).
There are several ways to run battles in GURPStech. Option #1 is useful if most players are BattleTech veterans but new to GURPS. Option #3 is best for veteran GURPS players who prefer the advanced combat system. Option #2 is a compromise, and is best suited for campaigns with more roleplayers than wargamers (#2 is what I normally use). Option #4 is handy for large-scale combats. Option #5 uses the GURPS mass combat system.
- 1. BattleTech variant (10 second rounds)
- Run the combat according to BT rules, but use 3d6 GURPS skill rolls rather than BT 2d6 Piloting/Gunnery rolls. Use BT rather than GURPS modifers, but double them (ie, a -3 becomes a -6). Also remember that in BT, modifers are opposite from GURPS: a '+' is bad, a '-' is good. Apply a +6 at short range, a +2 at medium range and a -2 at long range for to-hit modifiers.
On a GURPS Gunnery critical hit, roll on the BT Critical Hit Table, even if armor remains on the location. (This is adapted from R. Ostorero's rules in
- 2. BattleTech-style combat (10 second rounds, no map)
- Roll a Contest of Skills using each mechwarrior's Battle skill, using any appropriate modifiers for surprise, terrain, unusual tactics (see p.S92).
- The winner may fire first with no Accuracy or Targeting Computer bonuses, or last with them. The loser gets no Accuracy or Computer bonuses.
- Handle the rest as per option #1, above, though the GM should use any GURPS rules he feels appropriate (the BT hit location tables, GURPS ranged weapon chart, etc.). However, even though the round is 10 seconds long, the mechwarriors (re)act as if it were a 1 second GURPS round with regards to attack and defense options.
- 3. GURPS-style combat (1 second rounds, mapped)
- Treat 'Mechs as very large people (not entirely realistic, but neither are battlemechs...). 'Mechs are big targets, but get no bonus to hit other 'Mechs and vehicles -- that's what their targeting systems are optimized for (hitting a lone infantryman, however, is -4).
GURPS Vehicles will also be of great help.
Also, note that BT armor is ablative. Any shot that hits (even if the damage is less than the DR), reduces the 'Mech's DR by (damage rolled/10).
- 4. Abstract combat (based on GURPS Compendium II, using the starship rules)
- Use the following changes and additions:
- Contest of Tactics: The average Dodge score of each side is applied as a modifier.
- Survival: Use the pilot's Battle Skill, not HT, for these rolls. The degree of damage and Combat Reflexes both modify this roll. Replace the ship size modifiers with the 'Mech size modifers below:
- infantry: -6
- battlesuits: -4
- 10-30 tons: -2
- 35-65 tons: 0
- 70-100 tons: +2
- jumpship: +4
Sample 'Mech Damage Tables
These are mainly for the Abstract Combat option (#4 above), but can also be used in other situations.
||cargo area rattled
||ammo supply of one weapon destroyed
||one weapon rattled: 1/2 Firepower (or Malf 15 and Acc 0)
||mech rattled: all rolls at -1 for rest of battle
||gyro rattled: -1 to Dodge next round
||cockpit rattled: -2 to rolls for rest of battle, *
||leg actuator damaged: -1 Dodge, -1d6 mph cruising speed
||arm actuator damaged: -1 Firepower of weapons in/on arm
||engine rattled: -10% speed
||cargo area damaged
||jump jet destroyed: -30 yards to jump range
||ammo for one weapon explodes, *
||mech rattled: as above, but -4
||gyro damaged: -1 Dodge until repaired (if reduced to 0,a roll is required each Combat round to avoid falling)
||cockpit damaged: as above, but -4, *
||heat sink knocked out: -2 to Firepower
||leg actuator damaged: 50% speed, -1 Dodge
||arm actuator damaged: any weapons in arm cannot be used,nor can the arm
||engine damaged: reduce speed by 25%, roll 12- each round to avoid engine shutdown
||cargo area destroyed
||weapon destroyed, *
||gyro destroyed, *, @
||engine destroyed, **, @
||cockpit destroyed, **, **
||computer destroyed: all rolls at -8, *
||leg destroyed, *, @
||mech explodes, **, **, **
*, ** See p.CII104 for explanation. @ = 'Mech immediately falls over.
Mechs as cargo: Weight is as BT tonnage (while this is metric tons, and GURPS uses English tons, it's close enough). Volume is roughly (tonnage*35 cf) which includes all subassemblies (see GURPS Vehicles), though non-humanoid 'Mechs are usually less. This includes waste space, so reduce volume by 25-35% if the 'Mech is carried strictly as cargo (and not to be deployed from its bay).
Mechs vs Starships: A 'Mech gets a +1 to its DF for size, but is at a -4 in the Contest of Tactics (-2 if a LAM) due to lack of maneuverbility.
Shooting at Infantry
As noted above, 'Mechs are -4 to-hit people. However, it doesn't take much to kill an infantryman. A critical hit or a hit made by 10+ is a direct hit; remove the smoking boots from play. Any other hit places the round (or ray, or missile) 1d6 yards away per 100 yards distance (about 3 BT hexes) from the 'Mech to the target. PPCs do only 1/10 damage. For ACs and MGs, use the strafing rules from GURPS High Tech. Lasers do no damage except on a direct hit. Missiles doe 1/2 damage on a near-hit.
Infantry can shoot back, at a +4 to-hit.