Combat System
I am running a "homebrew" combat system made up of the ABTP, HB11 attack tables and Martial Law Crit and weapon tables. This was not an attempt to make the worlds most complicated system, rather i wanted a system that rewarded the use or armor (im Australian so the spelling is correct here) and made the choices of armor carry consequences. Added to this i have made a location system that randomly determines the hit location (inverted D100, the ones dice determines the major location and the tens determines left or right essentially)
This boils down to two rolls, one attack (and also determines location) second crit if any (All crits if multiple use the same roll).
To help the flow of the game i have created an EXCEL based calculator that determines the results of the attack and combined critical effect.
At the beginning of each encounter the players roll a combat perception (difficulty varies) to see if they notice any weaker points in the enemies armor (or a normal perception if they spend the round), and allow a "called shot" which is added as a penalty to the OB to adjust the hit location. They may learn thought the encounter if any specific hits hurt more.
A couple of other combat based touches, stun always means you go last in the round, only really means anything if your trying to do something other than parry.
Something i didn't mention was that the Crit modifier is adjusted for the class of Crit.
Currently I am using T=-10, A=+0, B=+10, C=+20, D=+30, E=+40, these are added to the crit roll instead of the listed values in the HB 11 attack charts.
You could adjust these values change the how lethal the game is.
The Hit location chart as below used inverted 1D100, eg swap the tens and the ones, it distributes the hit locations all over the body. I allow a penalty to "aim up" to hit a specific location. In true HARP style ill include an example,
1 Head
5 R Foot
10 L Foot
15 R Leg
20 L Leg
30 Groin
40 Abdomen
50 Torso
55 R Hand
60 L Hand
65 R Arm
70 L Arm
75 R Shoulder
80 L Shoulder
90 Neck
96 Head
Say the unmodified attack roll is 64, when looking at the location chart, read it as 46, which will be Abdomen strike, lets say the defender is wearing a chain shirt, If the attacker stated they wanted to aim for the right arm, as it is unarmored, they apply a penalty of 20 to the OB (i step in lots of -5) to make the 46 a 66, which brings it into the threshold for the Right Arm, but changes the attack table from Chain to None.
One thing i forgot to spell out (most of you will have already thought of it) don't forget to adjust the DB of the defender removing the DB for the BASE armor type.
The ABTR rules are spot on for calculating the DB values of higher quality/magical armor. It does take a bit if you are working out piece by piece for different materials.
Basically for a suit,
Soft Leather -20
Rigid Leather -30
Chain Mail -40
Chain and Plate -50
Plate -60
Bonuses for well made or magical material are added the the DB. One of my players has a Dragon Scale Shirt, which is Rigid Leather +20, the rest of his armor is Master Crafted Supple Soft leather, which after removing the shirt component provides an additional DB of +5 giving a total DB modifier (for armor) as +25. I don't separate the DB by location, thought it something i've thought about, balancing simplicity against "realism"