The A models came with the flashlight built in. The A model was taller due to the carrying handle with built-in flashlight. The B model had a removeable flashlight attached to the left side with a folding carrying handle ala FN FAL. Also the front side was of the rear folding variety. The B model also has an additional operating handle on the left side of the receiver. Most of the other differrences (aside from above) between the A and B models were changes to the upper barrel housing.
As this is a bullpup design, it is not an ambidextrious weapon. It is designed for right-hand firing only. The B model was designed for one hand firing with the additional operating handle.
The major detraction in this weapon is that an extended magazine was never factory produced. Though Choate made an aftermarket extension for the B model.
Overall the B model is more desireable in my estimation.
As an aside, the Model 10 series is based on the Supermatic actions.
