One Shot Stops

...And GURPS.

Common self defense ammo...  Let's go from small to big.

.25 ACP.  The smallest unless we count .22 LR, but there's not near so many actual concealable guns for the rimfire as .25.

.25 ACP pulls 1d pi-.  Center mass hits are body hits, so that's 1-6 raw damage, so 1-6 damage to penetrate then divide damage by 2 (round down min 1), so 1-3 points of damage vs the average of 10 HP.  Not even a major wound!

Changing to hollowpoints bumps the pi- to pi; but adds a 0.5 armor divisor.  That also makes normal clothing be DR 1.  That gives us 0-5 for reals now!  Now we have a chance to get a major wound.

On average vs the body: .25 ACP ball does 1 point and hollow point does 2.

.32 ACP is next.  2d-1 pi-.  1-11 raw damage.  1-11 penetrate then is divided in two for 0-5.  HP negates the pi- for pi and there's the DR 1 for normal clothes: 0-10 penetrate.

On average vs the body: .32 ACP ball does 3 points and hollow point does 5.

.380 will depend on the barrel length.  Short barrels like a SIG P238 get 2d-1 pi and longer barrels like a Colt 1908 Pocket Hammerless get 2d pi.

Short barrels get 1-11 that penetrate and stay 1-11!  While HP gets bumped from pi to pi+, the 0.5 armor divisor still lurks in the shadows (0-15 can penetrate).

On average a short barrel .380 ACP gets 6 points and HP gets 7.  An aside here, the similarity in damage between ball and HP was actually noted in a recent ballistics gel test of .380 rounds!  Go GURPS!

Long barrel .380's get 2-12 with ball (1-16 with HP).  pi+ with HP and the divisor.

On average that gets us 7 for ball and 9 for HP.

.38 Special from a snubby is 2d-1 pi and gets the exact same effects as a short barreled .380.

.357 Magnum from that snubber or 9x19mm from a full sized automatic is 2d+2 pi.  Ball 4-14 and HP 4-19!

Averages 9 for ball and 12 for HP.

Smaller 9mm's only get 2d+1 pi.  3-13 damage that averages to 8 for ball and 2-18 that averages 10 for hollow point.

Unorthodox rounds like .357 SIG and .38 Super get 3d-1 pi.  2-17 damage; averaging 9 for ball and 1-24 averaging. 12 for HP.

.40 S&W is an anomaly in GURPS.  2d+2 pi+.  Like all pi+ rounds damage that penetrates does 1.5x as much damage.  So it's 4-14 raw damage for ball that becomes 6-21 in tissue.  The hollow point bumps the damage to pi++ though, still with that damned armor divisor for 6-26.

Average damages will be 13 for ball and 16 for hollow points.

The beloved .45 ACP is a "mere" 2d pi+ for ball.  2-12 that becomes 3-18.  Averaged out, it's 10 for ball and 2-22 averages to 12 for HP.

Now that we've done all that math!

5 points of damage is a major wound on a typical ST 10 10 hit point person.  That means they're likely stunned and knocked down because they only have about a 50% chance of avoiding it with such a non-PC HT score.  Plus, any bullet that manages to do more than 10 means another HT roll to avoid being knocked unconscious.

While the benefit of the hollow points seem marginal on average, they can make the difference in whether the target keeps fighting next turn.

SUMMARY

Round -      Dmg - Ball, min - avg - max; HP, min - avg - max.
.25 ACP - 1d pi-;       0, 1, 3                     --             0, 2, 5.
.32 ACP    2d-1 pi-;   0, 3, 5                     --             0, 5, 10
.380 ACP  2d-1 pi;     1, 6, 11                   --            0, 9, 15
.380 ACP 2d pi;         2, 7, 12                   --            1, 9, 16
.38 Spcl 2d-1 pi;         1, 6, 11                   --            0, 9, 15
9x19mm 2d+1 pi;       3, 8, 13                   --            3, 10, 18
9x19mm 2d+2 pi;       4, 9, 14                   --            4, 12, 19

.357 Mag 2d+2 pi;      4, 9, 14                   --            4, 12, 19
.357 SIG 3d-1 pi;        2, 9, 17                   --            1, 12, 24
.38 Super 3d-1 pi;       2, 9, 17                   --            1, 12, 24
.40 S&W 2d+2 pi+;    6, 13, 21                 --            6, 16, 26

.45 ACP 2d pi+;         3, 10, 18                  --            2, 12, 22