Only the Mustang Mk.Ia had cannons. 54 of the number built were retained by the USAAF. Two of these served as the airframes for the XP-51B conversion.
P-51A serving with the 1st Air Commando Group in China....

Mustang Mk.I with chin guns.

Mustang Mk.1a with four Hispanos

P-51 (no letter designation applied). 54 retained by USAAF.

Mustang Mk.II, chin guns deleted (very similar to P-51A).

A-36A. Same gun installation as Mustang Mk.I, with dive flaps added.

XP-51B-2 (second of two converted to Merlin).

Mustang X and XP-51B-1 (first of two converted to Merlin).

One of two XP-51Ds, converted from P-51B airframes. Bob Chilton at the controls.
