Danny
A little research leads me to the following.
Photo of a Harvard with bomb racks in an article here:
RAF in Africa :Bob Aitken
Article also states (Guns (or Gun) was carried close to the wing root in the starboard wing in training roll for target practice on the ranges).
Also mentioned in piece from book "Britain's Small Wars"
1340 Flight was commanded by Sqn Ldr CG StD Jeffries, DFC, operated out of Nanyuki Airstrip 1953-54 (and possibly later). Equipped with Harvards modified to carry 4 x 19lb bombs and with one wing-mounted .303 machine gun. The flight had 8 - 10 of these aircraft which had been used for second-stage flying training in Rhodesia, and initially the pilots were made up from the flying instructors.
The flight operated in a local variation of 'close/tactical support' carrying out recces and ground attack missions against Mau Mau gangs in the 'Prohibited areas', mainly the Aberdare and Mount Kenya forests. Such attacks were usually made on information from ground forces or the Kenya Police Air Wing, a section of which also operated out of Nanyuki.
..and finally a line drawing of an AT-6C with machine gun mounted behind the rear cockpit. Here:
http://www.skytamer.com/NAA/AT-6C(side).jpg
Enough for today as my other half says I should be outside picking beans, which I'm off to do!