Introduction: I have fond memories of first edition D&D, but those memories do include a host of house rules. One aspect of the game that generated a lot of interest in house rules was the pace of combat. Without feats and other such innovations common to later editions of D&D, physical combat in first edition could be particularly stale as there just weren’t many ways to generate extra damage, even at high levels. Spell casters had options, of course, and specialty classes such as Thief or Ranger could generate extra physical damage under the right circumstances, but for basic fighter types, a fight with a big monster meant whittling them down slowly.
This is what had a lot of us experimenting with called shots. My own friends and I tried a lot of things, mostly variations on a penalty to hit roll in exchange for the possibility of a one-shot kill (or some comparable effect likely to take the intended victim out of the fight). Balancing the cost of the penalty against the benefit of a successful called shot was of course difficult. If the options for a called shot were too generous, even the biggest enemies went down with ease, and if the GM decided to turn that possibility on the players, then a TPK was just a few die rolls away. If the called shot option was too stingy, then you had to slog your way through even mediocre opponents, the game slowed down, and everything got tedious.
Really tedious!
In any event, what follows is the system I ended up with after a couple decades running first edition D&D. I really think this hit the sweet spot for my gaming group, but a lot depends on other factors in the game. We had a system for extra proficiencies, and we used special abilities and problems, both of which also contributed to slightly more dangerous player characters. In combination with those systems, our rules for called shots helped us to speed up the game and boost the power of physical attacks without completely obliterating the core system.
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Called Shots and the To-Hit Roll: At its core, the system calls for a simple penalty of -4 on the attack roll for any called shot. (If the call was hyper-specific, then GM could boost the penalty to -6 or even -8, but that was her call.) Along with that, a natural 2 becomes an automatic miss, although it does not become a critical fumble. If a called shot is successful in striking the target, the damage is treated as applying directly to a focused body-part. This can be called out (E.g. a head, a leg, a tail, or a player can just declare that they are taking a “Kill shot”). Either way the damage is now measured against 20% of the target’s total hit points (rounded high). If the damage equals that percentage or exceeds it, there is a chance, the called shot succeeds in destroying the body-part in question.
Chance of Success: The chance for success at this point is equal to twice the damage done on the attack or 5% per stage on the to-hit charts from the DM’s Guide, whichever gave the attacker a better chance of success. (Note that the highest stage of the to-hit chart for fighters would be 55%, and at least in our old games, the best fighters could generate damage in about the 20-30 point range on a single attack, thus making it a toss-up as to which chance worked best for a given attack.)
It is best for players using the option to write the percent chance of success based on the to-hit chart on the character sheet. This should enable a player to compare the chance using double damage versus the chance based on the to-hit chart quickly.
Successful Called Shots: Success generally meant death in the event of a “kill shot” or in the event of a specific called shot with lethal implications (e.g. a head, in most cases). Results such as decapitation which might be necessary to kill certain monsters could also be achieved in this manner (assuming the appropriate weapons). If a leg, an arm, a tail, or a wing had been the focus, it was generally considered severed or otherwise destroyed and the GM would apply whatever penalties seemed best to the maimed character as a result of the injury.
Failure: In the event that a called shot was not successful, the damage was scored normally against the target’s hit points.
Target-Based Limitations: Called shots were useless against any target that lacked meaningful anatomical vulnerabilities (e.g. an ooze, a zombie, or a ghost). Such creatures were simply not venerable to called shots.
Tactics-Based Limitations: Certain damage effects were not applied to called shots, or they were applied in unusual ways. Thieves and Assassins could either add their backstab multiplier to the damage of a called shot or apply it as a multiplier for a normal shot under the normal rules, but the player had to choose. (Most chose the latter.) Rangers add their giant-classed bonus to the damage, but leave it out for purposes of calculating the odds of success on the percentage die roll.
Dragons in first edition D&D suck. The narrative blows them up big time, but they are easy as Hell to take down. I recall an episode of Dragon Magazine tried boosting their power by adding minor attacks such as wing beat and tail swipe, but the damage for these was miniscule. Even with these additions, Dragons in first edition never lived up to the hype. They were supposed to be bad-ass, but they always ended up being meh.