We were just playing with that the other day, with me as my archer and the other player with 100% RPD. True to what has been said, it reflected all of the damage.
The thing you have to watch out for, and the reason that it isn't very popular, is that the reflected damage takes effect before the original damage, which makes the person with the RPD armor the aggressor, and frequently subject to murder counts.
That, and it only reflects physical damage, so other forms of damage (fire, cold, etc) won't reflect.
But it's great fun, and I'll be working on building up my own suit in the near future.