[Anthony]

The problem with the GURPS damage model is that it's trying to use a single DR value for multiple different armor and weapon types. This is an understandable simplification, anything realistic is going to be hell of complicated, but it means you get anomalies. Notably, flexible armor has somewhat different thickness scaling than hard armor, and also has variable protection with projectile velocity. A truly realistic assertion for the protection of level IIIa armor is that it stops the attacks it's rated as stopping, and no reliable statements can be made about its performance against other attacks.