OBT Forum

Over the years of playing BT I've worked up a lot of house rules, ripped them apart, started them again from scratch, dropped some, added some... etc.

I'm trying to settle on a set that I'm content with, with the following criteria being my main motivation for doing it:
* Adjusting aspects of the game which are too easily abused/power gamed
* Changing aspects of the game that seem counter-intuitive
* Avoiding overcomplicated rules
* Making things that I think are imbalanced more balanced/useful in some way without blowing the entire BV system apart
* Adding some little quirks just 'cause I think they're cool

(I haven't kept up to date on rules since the BMR, so I might be conflicting with stuff since then that I haven't come across yet)

Piloting!
Disarmed ‘mechs:
A ‘mech that has lost one arm is left with a hunk of dead weight on one side, or a complete absence. In either case, the balance of the ‘mech is severely impaired. Once a ‘mech has lost both arms it may have regained equilibrium but without any arms to control balance it will still struggle to stay upright.
One a ‘mech has had at least one arm disabled (internal structure gone, side torso disabled or limb blown off) it suffers a +1 modifier to all piloting roll difficulty.
This does not apply to armless ‘mechs, which are calibrated specifically to function without arms.
Purpose: Arms serve a purpose!

Knockdown:
Larger ‘mechs are not as vulnerable to being knocked down as smaller ‘mechs. In addition some weapons have much less physical impact force on the target.
Count only half of the damage from energy weapons towards knockdown.
The damage factor to be knocked down (normally 20) varies with weight class. If a 'mech suffers at least this much damage in one phase it must make a piloting roll to avoid falling down. For each full multiple of this amount of damage that a 'mech takes in one phase, the target suffers a +1 penalty to their piloting roll check to avoid being knocked down.
Light   10
Medium   15
Heavy   20
Assault   25
Purpose: To give heavier 'mechs a small advantage, and give energy weapons some different attributes.

Area control:
A 'mech that is prone or immobile (eg from being shutdown or having an unconscious pilot) does not exert control over it's hex and other units may pass through freely. They must have enough MP to both enter and leave the hex to do this, they may not end their hex in the same hex as an enemy 'mech whatever condition it's in.

Rush:
A vehicle or 'mech may attempt to enter a hex controlled by an enemy 'mech, but, like above, they must have enough MP to leave as well and must not end their movement in a hex occupied by an enemy 'mech.
To pass through the target hex both pilots make a piloting skill check. The "attacker" is the unit attempting to enter the hex of the other 'mech, which is called the "defender".
If the attacker is moving backwards, they suffer a further +2 penalty to their piloting roll on top of any other modifiers.
Defender piloting skill roll...
fails: No effect
succeeds: Attacker may make a physical attack against the defender immediately (either two punches, a kick or a club/hatchet attack as normally available - this does not affect their ability to make other attacks in this turn)
Attacker piloting skill roll...
fails: Attacker fails to pass through the hex and is placed back in their starting hex
succeeds: Attacker successfully passes through
Purpose: Hexes are 30 meters wide, it should take some effort to control that. Also, area control can easily be abused. Obviously if a light 'mech is blocking an assault 'mech, the threat of being attacked is not a great one and a larger 'mech can if it wishes just keep trying to pass through and weather the attacks for rushing through controlled areas. This seems fitting. A 20-ton 'mech should not be able to stop a 100-ton 'mech easily!

Gunnery!
Energy weapons:
Energy weapons have some advantages over ballistic or missiles weapons, the most notable of which being that there is very little delay between firing and hitting. Owing to this, any target movement penalty is reduced by one.
On the other hand energy weapons are severely affected by atmospheric conditions, however. Each +1 targeting modifier incurred by snow, rain, smoke or dust on an energy weapon attack reduces the damage of the shot by 1. In the case of energy weapon shots with multiple hits, each hit is reduced by the same amount.
Purpose: This gives energy weapons a different "flavour" to ballistic weapons, rather than them just being a weapon that does a different damage. Also, this facilitates the following rule.

Targeting computers and ballistic weapons:
Ballistic weapons gain much more from a targeting computer than energy weapons do. Since there is very little in the way of target leading for an energy weapon, the targeting computer only helps with pinpointing the target. With a ballistic weapon however, a targeting computer assists in leading the target and compensating for movement as well. All attacks with ballistic weapons that are slaved to a target computer reduce the target movement modifier by one.
Purpose: It's very inefficient to use a targeting computer with ballistic weapons owing to their high tonnage. This gives them an added bonus, making combining targeting computers with ballistic weapons more viable.

Margin of success:
The margin of success of an attack has an impact on how effective the attack is.
If the attack roll exceeds the target number, then the margin of success (MoS) is the amount by which it exceeded the target number. MoS can be used in three ways:
If an attack fires multiple shots, the margin of success is added to the result on the missile hits table for the attack (roll the dice for the missile hits tabel result, then add as much MoS as the attacker wishes to the roll, there is no advantage to increasing the roll higher than 12).
If the attack only fires a sigle shot then the margin of success is instead added to any resultant rolls on the critical hit table. If no rolls on the critical hit table are called for and the MoS is 8 or more, then a roll on the critical hit table may be made anyway! Add any MoS above 8 to this critical roll.
The attack may "shift" by one location in either direction along the damage transfer arrows for each 4 MoS (or if desired, the attack may be moved from the head to the centre torso but not the other way). It may only be moved to locations that are visible to the firer (if the target is in partial cover, this may be used to avoid hitting the cover). For attacks that hit multiple times, the number of allowed shifts must be divided between all attacks.
Purpose: Makes easy shots at low TN more dangerous, easier to hit with multiple shots at close range for example, and combines neatly with called shots below to merge everything into one system. Also mechwarriors are no longer wildly shooting at the target and try to hit something important when they can!

Called shots:
Before making an attack, the attacker may declare to be targeting a specific location. The head may not be the target of a called shot. This imposes a +2 TN penalty. If the attacker is using a targeting computer, the TN penalty is only +1 rather than +2.
If the attack hits then MoS must be used to shift the hit location towards the chosen target, but only takes 2 MoS per location shifted rather than 4.
Called shots may be made with punches and kicks normally, the attack may only be shifted to a location it could normally hit.
Note: This overrides standard called shot rules entirely.
Purpose: Makes called shots less wasteful and ineffective, but still not easy to achieve. Eliminates extra rolling for called shots. Combines neatly with MoS above. This will obviously make combat more deadly, but it always seems strange when my mechwarriors seem intent on sandpapering all of the target's armour off rather than going for a damaged spot.

Rear attacks:
Very few 'mechs have cockpits that face towards the rear, but most 'mechs have vulnerable spots on their backs. An attack that hits the head of a 'mech from the rear instead is treated as if it rolled a centre torso (critical) result.
Purpose: None really. Just a cool little tweak. Also allows you to shield your 'mechs head, if you need to, at the risk of exposing rear armour.

Criticals!
The amount of damage inflicted upon internal structure by an attack modifies the dice roll to determine critical hits as follows. Keep in mind the modifiers to the critical roll from MoS too.
Damage: Modifier
0-2: -2
3-5: -1
6-10: +0
11-20: +1
21+: +2
Purpose: Makes heavy-hitting weapons more likely to inflict critical damage.

Non-equipment critical hits
Empty critical slots/internal structure criticals
If a critical hit result strikes an empty critical slot or a critical slot containing structural components that would normally indicate a re-roll (eg endo steel) then instead of re-rolling the hit will strike a weak point, inflicting an additional point of internal structure damage.
If a slot that is already damaged is hit then just treat it as an empty slot so a point of damage is again applied to the internal structure. Any extra damage applied to structure from this will not result in further critical hit rolls.
Purpose: This stops ‘mechs with only a single ton of ammo in a location actually being more vulnerable than a ‘mech with the ammo tucked in with other components (like engines, or cockpits, which actually makes it safer to keep ammo with these vital components!).
Damage to destroyed locations
If a weapon attack hits a destroyed location, it simply hits the destroyed location. The same applies if it hits a location that is missing (except the shot misses). For the purposes of campaign games critical hits should still be applied to a disabled limb, but in one-off games this will not apply unless the target location has unexploded ammo boxes, which could go off and cause serious harm.
Purpose: I've never quite understood the whole "damage transfer" thing really. Also, with the MoS system it will be much less likely that you keep hitting destroyed locations.

Less explosive ammo
Weapon damage is based on a shot hitting directly against the target, the undirected explosion inside a ‘mech is devastating but not as focused as when the ammunition is used intentionally. All ammo explosions inflict half the damage of the exploding ammo.
Ammo explosions do transfer damage to the next location, but only half (round down) of the remaining damage transfers. A lot of the explosive power escapes out of the 'mech.
Purpose: To make ammo explosions less totally fatal, by standard rules it's largely a case that ammo explosion = 'mech destroyed so you might as well skip the entire step of applying damage. It's possible (if unlikely) to survive them with this.

Heat!
"Ammo explosion" result:
If a 'mech has an "ammo explosion" result and fails the test to avoid it, then roll 1d6 and apply the result as follows:
1-2   take a critical hit to engine (topmost undamaged slot in centre torso)
3-4   take a critical hit to the topmost undamaged sensors (treat as 5-6 if sensors already destroyed)
5-6   take a critical hit to life support (take mechwarrior damage if life support already destroyed)
In addition roll for ALL ammunition in the 'mech that is capable of exploding, on a d6 roll of 6 that box of ammo is set off.
Purpose: This both makes high heat less suicidal for ammo-bearing 'mechs, and makes energy-based zombie 'mechs actually vulnerable to overheating.

Weapons that inflict heat damage:
All weapons that inflict heat on the target ADD the heat to the damage when firing upon non-battlemech units such as vehicles and infantry (any type). Salamander-type battle armor ignores this extra damage.
Purpose: To make flamers more effective especially against other unit types, which really are very vulnerable to heat.

Other!
Antipersonnel weapons:
Abandon the "roll d6" damage rules for antipersonnel weapons and all the other weapon-specific rules for shooting infantry. Instead weapons apply damage as follows to infantry:
Any machinegun/any weapon that inflicts heat   2x damage
Non-pulse laser/any gauss            Â½x damage
All other weapons            1x damage
Purpose: Less extra rolling. Infantry add enough complication as is.

A few weapon/equipment tweaks:
Flamers:
Flamers inflict both 2 heat and 2 damage.
Purpose: To make them less useless, and get rid of the whole "go for heat" thing, as if you can stop fire damaging your target somehow. They're still pretty weak though.

AMS
Instead of using up a number of shots equal to the roll, AMS simply uses one shot each time it fires. But AMS will not engage on any missiles fired at a range of 3 or less as it needs time to acquire targets and engage them.
Thunderbolts are shot down on a roll of (TB damage / 5) or higher.
Arrow IVs are shot down on a roll of 4 or higher. Subtract 3 from the roll, that is the number of hexes along a straight line towards the firer from the target to find the hex in which the Arrow explodes, firer chooses which hex in the case of a tie. They are only shot at if they are targeted at hex containing the Battlemech with the AMS.
A Narc pod (any type) is shot down on a 2 or more.
Treat AMS as a machinegun with a damage of 1 if used for direct fire.
Purpose: Makes AMS worth having rather than just being an ammo explosion in the facade of a defensive item, but with a small limit on it's use to balance it.

Narc beacon
Explosive Narc pods inflict 5 damage, not 2. Also, a Narc beacon gets 12 shots per ton rather than 6. All other Narc weapons get double the ammo per ton too.
Purpose: Mostly to make Narc make more sense and actually be worth having. 166kg pods? Even 83kg is a bit oversized just for a transmitter...

Inferno SRMs
Each Inferno SRM does 1 damage and 1 heat.
Purpose: Still effective, but not broken.