You can punch with a stump. I would say you deal more damage as you don’t need to worry about breaking fingers and all of the delicate bones of your wrist are gone. This means the solid stump hits the target. Hard. d8 or d10 anyone?skypirateking
So, there’s three issues here, one far less important than the others, so let’s start with physiology, and the reason I’m not sure if you can even throw a punch without your hand.
Your forearm contains two bones, the radius and the ulna. This structure is what allows you to roll your wrist, instead of having it locked into a single orientation. It also means your forearm is not as structurally sound as it might first appear. Your hand helps anchor the entire structure together. These bones can fracture, and the results are pretty nasty. I’m not 100% certain how much more vulnerable these bones are if you’ve lost your hand, but that is the structure holding everything together. This is a large part of why I said, “you can’t punch without your hand.” Now, part of that was just me being pedantic, (you can’t form a closed fist if you don’t have a hand,) but even an in-line strike with the stump would probably be out of the question.
The caveat for a prosthetic is, really, just speculation on my part, that you could set up some kind of shock absorbing structure around the stump, to take a hit, (and may have that for simple comfort), along with the prosthetic’s harness helping to hold the bones in place. But, like I said, that’s speculation.
I’m assuming when you say a d8 or d10, you’re using D&D as your metric (and, if you’re thinking Pathfinder, that is just a tweaked version of D&D’s 3.5 edition.) Now, it is possible that you actually mean some other roleplaying system, though most of the ones I’m thinking of off hand would convert that damage into some kind of hilariously disproportionate hit.
If you’re unfamiliar, in D&D, a fairly normal battle axe’s hit will cause damage based on using one eight-sided dice, plus any relevant modifiers. This gets abbreviated to 1d8, (or sometimes 1d8+STR, as the primary modifier you’re going to be looking at is derived from the character’s strength attribute.) So, literally this is suggesting that being punched by someone’s stump will inflict more trauma on the victim than burying an axe in them or stabbing them with a sword.
Some monsters will do 1d8 with their claws, and the Monk class (mystical, martial arts superheroes), will eventually gain the ability to hit that hard with their unarmed attacks. (In 5e this doesn’t happen until around level 11, which by D&D standards is mid-to-high level.)
If you came to me and said you had a Monk in D&D who’d lost their hand, but continued fighting using their psychic powers to offset the loss, cool. But, we’re also talking about a game system (and setting) where martial arts masters literally become so good at fighting that their bodies are considered magical weapons. (And back in 3rd / 3.5e, a monk would eventually transcend their humanity and become a supernatural creature in their own right.)
As with all D&D adventurers, the monks are fantasy superheroes, and they represent an entirely valid expression of that. If you want a character who becomes so good at unarmed fighting that they can literally punch a dragon do death, the Monk is there for you.
So, having your character swing, and connect with the force of a fire axe, just because their hand is missing is a little disproportionate. Normally, unarmed attacks hit for 1+STR, no die roll needed. (This used to be 1d3+STR. There’s also an attack of opportunity, meaning your opponent gets a free shot on you if you try to punch them, unless your character is specifically specced for unarmed combat.)
D&D’s damage model has a few issues. And, because D&D was so influential, those issues have expanded far beyond just RPGs, and that’s the real reason I’m writing this response.
D&D’s health system abstracts injuries into a single durability meter. This has become the norm for the vast majority of games with detailed combat systems. It’s not just RPGs, even things like Doom run off a damage/HP system under the surface. (You can see the player’s HP, but monster are also operating under those same rules.)
This is so ubiquitous, because it’s simple, efficient, and works. It allows the designer to clearly signpost victory and loss conditions; it gives the player an easy to read assessment of how well they’re doing, and the ability to make informed choices.
And that’s where its utility stops. You can’t take “damage numbers,” and really apply them in a real world in any meaningful way. The abstraction doesn’t apply when you’re dealing with real people. You don’t take 5 or 15 or 500 points of damage from accidentally cutting your hand. You now a cut on your hand, and while it’s not life threatening, it also doesn’t affect your ability to survive a serious injury a few minutes later. (Or, at least, probably doesn’t.) But, under a hitpoint system all damage is cumulative, applying to the same pool. Stubbing your toe makes you less able to survive a gunshot.
There is a specific problem with D&D (and again, this is not unique to D&D, but it is less common), endlessly inflating stats. From a character building point, this always kind of bothers me. There’s no concrete meaning for a given stat value (aside from the six attributes. Where 10 average for a human character.) This is especially true of of their maximum health, which can range anywhere from 1hp (realistically, you’ll probably never see a character with max health below 3hp) to over 360hp. (I say, “over 360,” because I know full well, it’s possible to pump the value far beyond that.”.
This creates a situation where many characters can be downed in one hit from a longsword at level 1, but by level 10, can reasonably shrug off multiple, solid hits, from that same weapon. A character approaching max level, could easily have more than 100 health (depending on their class), and suddenly, that 1d8 hit is pretty trivial. The character literally gets to a point where they can shrug off weapons that could, and would, kill them.
Using official stats from Wizards of the Coast (D&D’s publisher), it’s entirely reasonable that a level 20 fighter, can take at least four .50 rifle rounds to the face without dying. That’s not, “oh, their armor absorbed the hit,” or, “it was a glancing blow.” That’s you shot them in the head four times with an anti-material rifle, and they’re still alive (and are probably able to survive several more headshots.)
(Seriously, D20 Modern, which is a variant of 3.5, puts the Barrett M82 at 2d12 per hit, if it crits that doubles to a maximum possible 48 damage per hit, meaning if your fighter has over 200hp (which is likely), four consecutive headshots are survivable. If it doesn’t crit, and you’re not getting max damage rolls, you could easily dump an entire mag into to fighter without killing them. And, if you’re familiar with D20 Modern, yes, that version has a level cap of 10, at which point we’re still talking about multiple headshots being survivable.)
Now, D&D tries to walk back some of this insanity with suggestions like the blow not penetrating armor, or skill developing to a point where the character knows how to avoid serious injury. However, the math doesn’t work, and hitpoints will (almost) always devolve into bizarre edge cases.
The problem isn’t D&D. While its implementation has issues, and various designers are always trying to, “make it more realistic,” which is a bit like slapping a band-aid on four .50 headshot wounds, the system itself can make for compelling experiences. Just, be very cautious about taking them out of that context.
The great strength of HP systems (beyond it being easy to read) is that it helps mitigate the extremely unpredictable nature of combat. (I’m not going to delve into concepts like, “exploding dice,” which exist in some games), but in most cases you can easily predict the worst possible outcome in a given combat situation governed by an HP system. (For example, being able to calculate the average and maximum possible damage from the sniper rifle example above.)
The issue is, that’s not how damage works in the real world. People can, and do, die from relatively minor injuries. A light blow to the head can result in a cerebral hemorrhage, which will kill you. A relatively light strike, at a bad angle, can fracture bone. A punch to the kidney can cause you to internally bleed to death over a matter of days.
In a very strange, and counterintuitive sense, the way we think about damage is a fantasy. We’ve recently had the longsword/rapier discussion floating around, and that’s an excellent example of how damage doesn’t work the way you think.
In D&D, the longsword is a 1d8, while the rapier is a 1d6, (technically, 5e finally changed rapier a d8, but for almost 40 years, it did less damage.) In the real world, both weapons are quite capable of ending a combatant’s life in a single hit. It doesn’t matter if you just picked up the blade for the first time, or if you’ve been dueling with it for decades. In D&D (barring special circumstances) it is impossible to kill a high level character in a single strike from either weapon.
The idea of breaking down damage to a number (or linear value) only works, when there’s no actual people involved. Damage suffered is a consequence of applied Newtonian physics, not arithmetic.
Hit point systems struggle when it comes to converting those numbers into detailed injuries. (Or mechanical damage when one of the participants is an object, rather than a living being.) For a writer, this is a huge problem.
As a writer, hit points are not useful on their own. You can’t write, “my character took 15 points of damage and was knocked prone,” while expecting it to carry the same weight, as your character getting kicked in the side, losing their balance, and falling into the mud, before taking a boot to the face. (I’m now reminded of that novel where a character uses an AoO to activate circle kick, and the really was just one step removed from identifying each action by the D&D terminology.)
Again, I do like D&D for what it is. I think it is a very good, cooperative, tabletop, strategy game. As a roleplaying game, it’s not my favorite, but that has more to do with your group and DM, and I’ve had a few terrible DMs over the years.
As a framework for a fantasy setting, I’m not overly opposed to D&D. Between the various campaign settings, there are a few that do some really interesting things with the genre. Planescape and Dark Sun still stand out as the highwater mark for me, and if you’re writing fantasy, you should probably develop a passing familiarity with both. Ravenloft has never been a favorite, but there’s a lot to recommend it. Dragonlance feels a little overrated in my opinion, but I suspect that’s because Hickman and Weiss’s novels carry the setting. Forgotten Realms is significantly better than it looks at a glance, but a lot of the interesting (post-apocalyptic) elements are easy to miss, and get lost. Spelljammer is weird, in a compelling way. Urban Aracana is debatably not a D&D campaign setting.
For understanding combat, or writing violence, D&D is not a good starting point. It is a slightly janky, but highly detailed squad-level, strategy game. It can be a lot of fun, and you can tell a fun story based on what the dice did to your friends, but any attempt to write a coherent narrative from it, will require you to spite the dice, rather than following their direction.
If you asked me to design a, “realistic,” damage system for a game, I’d probably lean towards more of an applied condition system. These do exist, but they’re somewhat rare because they require a lot of bookkeeping, and it can be difficult to assess how well a character is doing at any given moment. They also have the disadvantage that they can outright kill a character with little to no warning, and while that is true to life, and is advantageous in a narrative setting, it feels really bad when your character takes a dirt nap with no warning, due to events completely outside your control. (The best versions of this I’ve seen, use a shuffled deck of cards to inflict and track damage. Which opens up a lot of options for fine tuning damage consequences to the specific situation.)
To be clear, I don’t think that hit point systems are bad. I think their positives vastly outweigh their limitations, in a game. However, outside of games, hit points become actively detrimental. If you’re wanting to write violence, it’s something hit points are more of a hinderance than a help.