Ok thinking about the charts in rm they are realy made up of two parts. Crit and damage.
I think I have a good way to do crit without a chart but keep the same feel.
Ok here is the idea for ever 10 points you get to hit after factoring ob and db.
You get a crit point. You start by taking off 3 crit points(the point at where you would not hit with the weapon. Then you can spend the rest of you points to buy crits..
What I'm thinking is a=4,b=6,c=8,d=10,e=12
So a player rolls a 110 then he can pick 1c or 2a's.
This system allows for a 100% open end roll. Also based on the weapon you could changed the numbers needed for diffrent types of crits.
Armor would changed the number of crit points you would get. So plate would give you -8 crit points vs you.
More when I'm not posting from my phone. What do you guys think?