Ram: For instance, the ram I believe the gun would look better and functuoin way better if the ram were a red rod this way there woudl be less pressure on the (Piston wheel) you could also make the piston wheel have smaller radius ,witch would reduce the stress ,allow higher rate of fire ,and more power.
Barrel: If at this point anyone noticed I used the ZKAR's barrel and mag , Yes I did it was the most ideal system for a full auto knex gun. If you decide to use a red rod sized ram the barrel will need to be way smaller and also must shoot blue or even white rods. (this may be a problem)
Body: If you use the red rod ram the body will turn out almost half the size...
Gear ratios: there's no way to be certain how much tourq you will need but the slower you gear the spinning around the more power you will get from the ram. In other words It will take some testing.
(you'll need a bunch of red and blue gears to do this, at least 2 blue and prolly 10 red for the whole gun.
Power sources: the best power source you can get would be ether a custom motor and battery pack ,or a battery drill. (using the motor could give you many options where you want the handle )
Be creative I'm not the only one with ideas you could get some to!