Thursday is GURPS-Day, and I’m going to try and answer a question that +Jason Packer probably already answered for himself. But I write what hits me.

He noted in a post that there are ways to randomly hit lots of things in GURPS, but “chinks in armor” doesn’t seem like one of them. Are there any ways to hit the chinks or armor gaps in GURPS randomly?

I think formally, no. But practically, there might be one and one can squint the way to another.

The only RAW method might be that on a critical hit, it’s possible to roll a result that halves DR. That could easily be read as “you just hit the chinks in armor!” What that precludes is an actual defense – the only time this happens, it happens automatically, with your foe not able to parry, dodge, or block due to the crit.

The alternate might be to say something like “if you make your hit roll on a random location by X, then you hit armor gaps.” This X should be fairly large, since the basic penalty for armor chinks is -8 to -10, depending on what you hit. “Make it by 6-8” works for most locations, and since the penalty to hit a random location is 0, putting it as “make it by 8” is probably a decent way to go.

Edit: Chinks on the torso is -8; everywhere else is -10. “Make it by 10” and “score a critical hit” aren’t that different, so I don’t know if that’s a good option.

The best option to *get this done* easily is to grapple the guy (halving location penalties) and make a telegraphic attack, which brings you to -0 on the torso and -1 for everywhere else. Use a proper CC weapon. That doesn’t really address Jason’s original question (the random part of it), but it is a much higher percentage option for a difficult location. If you’re using Technical Grappling, you can skip the Telegraphic Attack and spend Control Points to lower the hit location penalty, too.

"Made it by X" is probably not good, because why aim for chinks in armor at -8 if you can aim for the torso at -0, and hit the chinks anyone if you make it by 8 and otherwise get a buffer of normal hits? It also encourages maximizing skill to up your chances of a chinks in armor hit while still maximizing your chance of hitting normally. Aiming for it would be for suckers. Even an additional margin just makes it a different tradeoff (-8 to hit it deliberately, but "make it by 10" to randomly hit it)

A second die roll might be a good way to go, but you'd probably want to just have a second 3d roll and figure the odds for that.

Might. I've used in my firearms-related games the rule that any torso hit made by 3+ hits the vitals anyway to good effect. A second die-roll is game-mechanically satisfying, and in terms of theory I don't disagree with anything you said. I suspect, though, that the right way to hit chinks in "real" combat is to hit them telegraphically, at -4 to the torso and -6 otherwise, and the defender will know you're doing it and be better able to protect those areas (thus the +2). Setup Attacks would be the way out of this, I suspect.

Anyway, as I note, game-mechanically you're right, and the step-down might be (say) assuming a 16- to hit the torso, which is 8- for chinks, for a 98% chance to hit dropping to 25%. For non-torso, 16 drops to 6, or 98% to 10%. Maybe chinks is 8- on the torso and 6- on the everywhere else.

Based on the range/speed chart, a -8 to hit is 1/21.5 the linear scale and 1/464 the area, but it's probable that any given target has multiple chinks. I'd actually be tempted by something like 'on a critical hit, you may bypass active defense [i]or[/i] hit a chink in armor, attacker's choice'.

I'd bypass defense every single time. Short of rapid-fire, defense completely negates damage while with DR there's always the chance of rolling high damage.

Not to mention the other effects of critically striking.

Remember, they still have to roll. Let's say I'm doing 2d and my target has DR 6. Average damage, after DR, is 1.56. Against DR 3, average damage, after DR, is 4.03. Therefore, if my target has a 61% or lower chance of defending, I'll average more by halving armor. 61% is approximately a (modified) defense roll of 11, and it's pretty common after deceptive attack for defense rolls to be 10 or lower. Against DR 8, it's better to halve armor unless defense is 13+. So, situational, but not always a bad choice.