Our glorious forum mod @Ardez did a experiment for this when I asked for exact limb shot damage long time ago,
but now I found out what’s the exact damage reduction rate after experiencing various weapon’s leg shot damage.
Damage reduction is exactly opposite to SNITCH, which is -25%.
It’s not really THAT important to auto-firing weapons, but it gives huge influence to harder hitting/single shot guns.
Grandeur does 30 dmg to the leg, so [b]you can still kill 110HP merc with two body shot or one headshot + leg shot,
but not 120 hp merc.[/b]
MOA does exactly 56 dmg to the leg, still able to kill 110hp merc with two leg shots. Thunder can sustain THREE leg shots of MOA.
Felix does 59 dmg to the leg, can not kill 120hp merc with two leg shots.
PDP does 34 dmg(33.75), which is same as S/W revolver. PDP is best female merc killer gun in this game, but you can’t kill 80/90 HP merc with two shots if you shot the leg one time.
Dreiss does exactly 20 dmg.
Didn’t tested all guns, by getting shot by other guns but well, besides all of that, moral of the story is
don’t shoot the legs as possible. 
You deal 8dmg with MK.46 to the leg! That’s basically Empire-9 XD
I will soon write a post about how effective the base damage(Raw numbers) of each weapons are.
Basically it is just calculating of how much over damage is caused.
For example, K-121’s 17dmg base dmg might leave 120HP merc alive with 1HP if you shot him 7 times.
17 x 7 = 119, so 16dmg is wasted.
Or Grandeur needs same three shots when killing 120HP merc and 90 HP merc.(30 over dmg caused. Very effective when shooting 120hp merc, but very inefficient when shooting 90HP merc.)
Cheers All Dbers !