Caliburn101
Explorer
I might as well ask you for the D&D stats of a bodkin arrow if you want to nit-pick... 

Nobody here has said that.their contention that guns act just like more primitive weapons against medieval armours of all types.
Nobody here has said that.
Don't split hairs on this eh?
Arguing that the AC contribution of physical medieval armours should make hitting a target more difficult with a firearm is supporting precisely this contention.
It's not really either. Or it's not very good at it. If D&D were emulating the S&S or High Fantasy or broader fantasy genres (at all well), it wouldn't have bandaid Clerics or Vancian casting (or possibly even PC casters), for instance.Reminder: D&D is a genre emulator, not a reality emulator!
Not so much. A human being, or even something a bit larger, can be transfixed by a sword, creating a through-and-through wound channel, just like a bullet might create. 'Primitive' weapons are plenty deadly. But pushing a sword through hardened leather or mail is no mean feat, while bullets won't have much trouble with that kind of protection (neither will heavy crossbow bolts, for that matter). 1e went there: it gave weapon vs armor type adjustments in detail, which'd also work fine to model firearms, I suppose. Going all the way to 'ignoring armor' is a simplification, and models a setting in which armor has been more or less defeated (there are times in history when armor is staying ahead of the weapons of the day, and times when it's been all but abandoned).Firearms having more kinetic energy than a sword thrust argues for them doing more damage than a sword thrust, not for them ignoring armor.
What you are describing is a difference in degree, not effect. A bullet (at least a modern one) has a lot more kinetic energy than a sword thrust (at least one by a man, but not necessarily a frost giant), so it will penetrate more material than a sword thrust from your average human. There is some other stuff involved--relative material hardness, shearing effects, but from an eyeball perspective, it's all the same thing, kinetic energy applied to a specific point.
To the extent 1e was accurate, it was modelling how much kinetic energy could bring to a specific point--a war pick and a rapier are both piercing weapons (ie energy delivered to a single point)--but a war pick is swung, so it builds up delivers more energy to that point than a rapier. A swung sword has more energy than a rapier, but it's spread across a blade instead of concentrated on a point. A swung axe is able to hold more energy because it's heavier (or has the weight concentrated at the point of impact). A gun just has more energy behind it. And 1e also was woefully mistaken about the stopping effectiveness of mail.
But firearms, especially primitive firearms, are really easy to model. There's no swing versus thrust, they aren't a fine point attack. They are essentially a hammer blow (GURPS actually lists firearms as bludgeoning attacks-accurately in my opinion). A blackpowder gun of the 15th through 18th centuries also had some issues that mitigated its effectiveness. Its ammunition was a soft lead ball about 3/4 of an inch across. So the kinetic energy it was delivering was spread across a much wider area than a sword or pick point. Likewise, it was a lot softer than the armor it struck, so it had a tendency to deform, spreading out the damage even more. Which is the point of armor--to spread out the point of impact.
You are right; leather armor won't stop a musket ball, just like your average bulletproof vest today won't stop a high powered rifle. But in both cases they will slow the bullet down. A bulletproof vest will often turn a bullet that would be a through and through into a hit that stops in the body. Leather would do the same thing, even stop some bullets at the limit of their range.
Point is there's only so much human to penetrate. Once you've created a through-and-through wound channel, you're done, the rest of your kinetic energy is spent down range.What you are describing is a difference in degree, not effect. A bullet (at least a modern one) has a lot more kinetic energy than a sword thrust (at least one by a man, but not necessarily a frost giant), so it will penetrate more material than a sword thrust from your average human.
Well, it did in its first edition. It changed to them being their own kind of damage - that was more effective against armor than bludgeoning. FWIW.They are essentially a hammer blow (GURPS actually lists firearms as bludgeoning attacks-accurately in my opinion).