A6M5 (Model 52) - 7.7mm Type 97 gun x 2; 20mm drum-fed Type 99-2 Mark 3 cannon x 2 (100 rounds per gun) (a bulge at the underside of the wing for each cannon's ammunition drum)
A6M5a Kō(Kou) (Model 52甲) - 7.7mm Type 97 gun x 2; 20mm belt-fed Type 99-2 Mark 4 cannon x 2 (125 rounds per gun)
A6M5b Otsu (Model 52乙) - 13.2 mm Type 3 gun (Rt. cowling); 7.7 mm Type 97 gun (Lt. cowling) --> asymmetric appearance to the top of the cowling. Armored glass on windscreen. Larger propeller spinner. Drop tank with fins. [from April 1944]
A6M5c Hei (Model 52丙) - 13.2 mm Type 3 gun (Rt. cowling, gun at Lt. cowling was removed). 13.2 mm Type 3 machine gun was added in each wing outboard of the 20mm cannon. Four racks for rockets or small bombs. Armored glass headrest. Drop tank with four-post design. [from Sep 1944 - for intercepting B-29]
A6M5-S (night fighter) - one 20 mm Type 99 cannon behind the pilot, aiming upward (no radar)
A6M7 (Model 62/63) - long range dive bomber, similar armament layout to A6M5c. [from May 1945]