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GURPS Third Edition came out in 1988. Fourth Edition in 2004.
We played it for all 16 of those years and we had a lot to unlearn when the new version came out.
How ranged weapons work, particularly firearms, was changed pretty dramatically.
First: Semi-Automatic Fire
In 3e you took your skill level, added bonuses for aiming, bracing, etc then subtracted penalties for range, recoil, target movement, bullet shyness, flinch and buck fever.
Our shooter's skill is 12.
Lets take three shots with an M16A1 at a man sized target at 50 yards.
Skill 12 + Acc 11 + Braced 1 - Range 9. Recoil is a -1 and does not apply to the first round fired.
First round; 15 or less. Second; 14 or less. Third 13 or less.
Let's make it a combat situation where the other guy is firing back and you know you have to make that shot! That adds in bullet shyness and buck fever. Both are -0 to -10 penalties, GM decides. I'll rule that they're -5 each this time.
Skill 12 + Acc 11 + Braced 1 - Range 9 - Bullet Shyness 5 - Buck Fever 5. Recoil is a -1.
First round; 5 or less. Second; 4 or less. Third 3 or less.
Harsh! We'll have Fuzzygeff come along and calculate the probabilities for landing a hit at all there.
4e:
Most of the lingo is the same. There's no longer a bullet shyness or buck fever. All shooting is now assumed to be under stress where the 3e assumption was at the range.
You now take skill level add bonuses for aiming, bracing etc and subtract penalties for range and movement. Recoil is a completely different mechanic. For each "Rcl" your roll exceeds the chance to hit, you get an extra round hitting!
Skill 12 + Acc 5 + Braced 1 - Range 8. Rcl 2.
To hit with 1 round you need to roll a 10 or less, two round on an 8 and three round on a 6.
It's worse than at the range and better than under mid range stress penalties.
Second: Automatic Fire
The rough formula is the same 3e except we now break the weapon's rate of fire (RoF) into "bursts" You make as many 4 round bursts as you can then the remainder is a less than 4...
The M16A1 has a RoF of 12*. The asterisk means its select-fire.
Let's fire the whole 12 at our target! It works the same as semi except we're rolling for each burst instead of each bullet and recoil applies to the first burst.
Skill 12 + Acc 11 + Braced 1 - Range 9. Recoil is a -1.
We get three 4-round bursts. Initial chance to hit is 14 and we look up how many shots hit on a table based on how well you roll. Miss by 1 is 1 hit, hit by 0-1 is 2 hits, hit by 2-4 is 3 hits and hit by 5+ is 4 hits. Second burst rolls against a 13 and third against a 12.
Now let's apply our stress modifiers.
Skill 12 + Acc 11 + Braced 1 - Range 9 - Bullet Shyness 5 - Buck Fever 5. Recoil is a -1.
Changes our rolls to 4, 3 and 2. Two is normally impossible, but since a miss by one is a hit, we'll let them try. Also note that missing by 10 or more is a critical failure!
I want to point out here and now that Buck Fever and Bullet Shyness were among the most unpopular rules my players encountered. Having your damn epic chance to hit whittled down to ammo-wasting pissed them off.
4e!
Skill 12 + Acc 5 + Braced 1 + Rapid Fire 2 - Range 8. Rcl 2.
To hit with 1 round you need to roll a 12 or less, two rounds on an 10, three rounds on a 8, four rounds on a 6 and five rounds on a 4.
When you consider the stress modifiers, a 3e character can only hope to land five rounds as well! The 4e character is far more likely to hit at all.
Third: The Snapshot Penalty
3e guns have a stat called "Snapshot" (SS). An M16A1's SS is 12. What this number means is if your chance to hit is 12 or less there's an additional -4 penalty to hit. This penalty is erased by aiming (which also adds the Acc bonus).
Third: The Snapshot Penalty
3e guns have a stat called "Snapshot" (SS). An M16A1's SS is 12. What this number means is if your chance to hit is 12 or less there's an additional -4 penalty to hit. This penalty is erased by aiming (which also adds the Acc bonus).
Skill 12 + Braced 1 - Range 9 = 4 which is less than 12 so another -4 bringing our chance to hit below 3; so no chance to hit! Notice that we don't even have the stress mods on there?
In 4e you simply don't get the Acc bonus.
Skill 12 + Braced 1 - Range 8. Rcl 2.
To hit with 1 round you need to roll a 5 or less, two round on a 3.
Finally: The Beaten Zone
Automatic fire is normally used as an area weapon not a point weapon. Machine gunners fire into what is called the beaten zone.
It's a lozenge shaped area where the bullets are going to pass through standing men.
In 3e they mention all that and don't help you with defining it.
So the GM gets to decide the area affected and the player starts rolling. Since it's not aimed fire at all, and the chance to hit 6 or less. You roll that for each round at each target in the area. Our M16A1 has a RoF of 12 and lets say there are 6 bad buys in the zone. 72! rolls! Actually it could be less. If a bullet hits something, you stop checking to see if it hits anything else. It takes forever and is a bookkeeping irritation of the first order.
This is the only rule that got more complaining than the stress modifiers.
4e replaces that tedious process with "suppressing fire". Same rules chances to hit as with normal automatic fire, except your effective skill can't be exceed 6 (8 if from a mount like a tripod). RoF 9 or less attacks everything in a fan two yards wide at the target's range. If you have RoF 10+ you can add an additional two yards per 5 shots and you have to put at least five rounds into each zone. RoF bonuses apply normally.
Dumping all 12 shots into one zone.
Skill 12 + Acc 5 + Braced 1 - Range 8. That's 10 or less which becomes a 6.
Skill 6 + Rapid Fire 2. Rcl 2.
Roll for each target in the zone.
To hit with 1 round you need to roll a 8 or less, two rounds on an 6, and three rounds on a 4.
Spreading into two zones... Six into each.
Skill 6 + Rapid Fire 1. Rcl 2.
Roll for each target in the zone.
To hit with 1 round you need to roll a 7 or less, two rounds on an 5, and three rounds on a 3.
There's still a lot of rolling, but it's a lot less. 6 rolls for six bad guys instead of 72, plus the zone is better defined. Downside, it attacks anyone in the zone, friends included.
Okay, I noticed this:
ReplyDeleteFirst round; 5 or less. Second; 4 or less. Third 3 or less.
Harsh! We'll have Fuzzygeff come along and calculate the probabilities for landing a hit at all there.
It's pretty easy. Multiply the chance of missing with each shot, and you have the chance of missing with everything. I get a 93.17% chance of missing all three shots.