I Have Forgotten How To Do The Math

There was something that former friend Anglave hated about GURPS 4e over 3eR.

4e has a single roll for the entire turn's worth of shooting, 3eR broke it down to shots/bursts.

He contended that you had a better chance of getting hits if you rolled the rounds individually.

With a Glock at 7 yards.  Skill 12.  RoF is 3 in both editions.

In 3e, Accuracy is 3, Rcl is -1.  Snap shot is 10.  -3 for range.

You get three separate rolls for the three rounds in 3e.

If you aimed that's a roll of 12, 11, and 10.

If you didn't aim that's 5, 4 and 3 because the snap-shot penalty is teh suxxor.

Aiming gets you, individually, 74.07%, 62.5% and 50% for each round.

Skipping the aim, losing the Acc and gaining the SS penalty gets you 4.62%, 1.85% and 0.46%.

The math I can't remember is the chance to land all three rounds.

IIRC it's multiplying the chances by each other and that's the final chance.

If I remember right that means a 23.146875% chance of getting three hits if you aimed.

But if you didn't!  Forget it.  You're statistically unlikely to get all three.

4e's stats are Acc 2, Rcl 2.  Same -3 for range; but no snap-shot penalty.

Without aiming your chance to hit is a roll of 9.  But if you roll well, a 7 gets two hits and a 5 gets three.

Your chances of doing that are 37.5%, 16.2% and 4.62%, respectively.

Aiming adds two to your chances for and 11, 9, 7 for 1, 2 and three hits.  62.5%, 37.5% and 16.2%.

If I did the math right, you are more likely to hit with three rounds after aiming in 3e than you are with 4e.

I don't think I did the math right.

But, without aiming, your are FAR more likely to land all three in 4e than 3e.