So I've been working on a 2d20 based system for a side project, and it's playing out as a hybrid of a roleplaying system and a simulation-heavy combat game. This means that the engine has quickly become hard to use; it's a game in which the player characters are all using battlesuits to fight fantastical science-fiction nemeses, but the problem is that modifiers begin to stack on characters very quickly-for instance, by the time one's in combat they're looking at up to 15 points just from their weapon, battlesuit, and training.
One thing I've tried to do to balance this back out is to make the combat heavily focused on per-bullet ammunition expenditure. Each shot fired causes recoil, and each attack is handled separately, with a quick and lethal system that focuses on putting down a ton of lead as quickly as possible. The idea is that one shot almost kills someone, and five is almost a guaranteed kill against all but (mini)bosses or PC's. However, I've found fairly quickly that what this means is that it turns into a sliding scale on the target numbers; the goal is to roll below a threshold, but that starter threshold may be up at 50 before sliding all the way down to ~15 or so with a really long burst of a heavy weapon spraying an area.
For the most part this is acceptable; player characters are effectively space ninjas, so there's no issue with them not missing with the first shot in any combat. However, I'd like to know if there's any example of people trying to resolve this sort of thing-having a guaranteed hit for your first several bullets and then a near-guaranteed hit for another two (worst case) or five (best case) is a mite much.
EDIT: To clarify, here's roughly how the system works.
The game itself is meant to mechanically model a video game; in such a way that it is possible to convert items from one to the other if their numerical values are known (the tabletop is "low-resolution" if you will, typically focusing on dividing these numbers).
The core system of the game is a 2d20 "roll under" system, with target numbers assigned somewhat arbitrarily. In combat, this is the enemy's Defense Rating, which varies from between 5 (really tiny, fast, annoying foes) and 35 (slow bosses).
To make an attack, players calculate:
- Their character's accuracy value. (Variable)
- Their weapon's accuracy value. (Variable)
- Their battlesuit's accuracy value. (Variable)
- Any other appropriate modifiers, such as movement, lighting, and distance. (Variable)
- Whether or not they're attacking multiple opponents, whether they are doing so in a single attack, or as multiple. (-5)
- A penalty for all prior separate attacks. (-5 per, but only for successive attacks).
- A penalty for all prior rounds fired, except for earlier rounds of the same short burst (-3 per, may turn into variable based on ranged weapon damage).
The weapons themselves have stats that will seem eerily familiar to anyone who's played any of the 40k RPG's, with an accuracy value, a damage value, and a range increment as well as their available attack rates (if multiple are available) and special effects (shotguns, for instance, have a special effect).
This means that someone firing a second attack with a semiautomatic weapon is facing a -8 penalty, but if they're attacking two foes they're facing a -5 on their first and a -13 on the second, making it progressively more difficult to hit as more lead flies through the air. For the most part I don't see it being too clunky, since most modifiers are pretty static, but that's a really large potential range (high-end weapons and characters may be looking at +15 accuracy, meaning they'd have a 50% chance of hitting even the most nimble foes in the game with a single attack).