BATTLETECH – How Accuracy Works
When you fire a shot, the percentage chance to hit is determined by three things.
- The base hit chance of 75%.
- Bonus of 2.5% per point of gunnery skill.
- Potential penalties from evasion, indirect fire, etc.
Let’s look at them individually.
The base chance to hit is 75%. That is, if you have a pilot with no gunnery skill firing a weapon with no bonuses at a mech with no evasion and no other modifiers, it will hit 75% of the time.
Next up is the gunnery skill. This is just a simple increase of 2.5% per point of gunnery skill which is added onto the base hit chance. So, 2 points of gunnery give 5% bonus and an 80% overall hit chance, 6 points give a 15% bonus (90% hit chance), up to a 25% bonus (100% hit chance) once you’re at gunnery of 10. So far, so simple.
Then for the third point, which is where things start to get more complicated. All other bonuses and penalties to accuracy are combined into a single number called shot modifier, which you can see if you mouseover a weapons chance to hit when taking a shot (in the bottom-right corner of the screen). A higher shot modifier means a more difficult shot, and a resultantly bigger penalty.
Positive shot modifier (i.e. a penalty to hit) can come from enemy evasion pips (+2 per pip), firing at light mechs, firing a weapon outside of its optimal range, indirect fire for LRMs, recoil for autocannons, etc.
Negative shot modifiers (i.e. a bonus to hit) can come from weapon accuracy bonuses (all energy weapons, or weapon+ with accuracy bonus), TTS mods, arm-mounted weapons, being inspired (morale above 50%), taking a precision strike, or being at higher elevation than your opponent.
However, overall shot modifier can never be negative. Even if you have multiple bonuses and no penalties, you will still end up with a total shot modifier of 0, which means no change to the overall accuracy.
To put it another way, your maximum possible chance to hit is determined exclusively by your gunnery stat. For example, if you have a gunnery skill of 6, then you will never see an overall chance to hit that’s above 90%, no matter how many bonuses you stack. All other accuracy bonuses can be used to offset penalties but will not increase your hit chance above your max.
On the other hand, if your shot modifier is positive, then that gives you a penalty to hit, with a bigger shot modifier equating to a bigger penalty. To be specific, 1-10 points of shot modifier give 5% reduced chance to hit per point, with each point of shot modifier beyond 10 giving a 2.5% reduced chance to hit per point.
As examples: a shot modifier of +6 reduces your hit chance by 30%, a shot modifier of +10 does so by 50% and a shot modifier of +14 does so by 60% (10×5 + 4×2.5).
