From Wikipedia:
By September 1942 Me 323s were being delivered for use in the Tunisian campaign, and entered service in the Mediterranean theater in November 1942. The high rate of loss among Axis shipping had made necessary a huge airlift of equipment across the Mediterranean to keep Rommel's army supplied.
On April 22 1943 a formation of 27 fully laden Me 323s being escorted across the Sicilian Straits by Bf 109s from JG 27 was intercepted by seven squadrons of Spitfires and P-40s, with the loss of 21 Me 323s.Three of the P-40s were shot down by the escorts.
In terms of aircraft design, the Me 323 was actually very resilient, and could absorb a huge amount of enemy fire, unless loaded with barrels with fuel – the Afrika Korps' nicknames of Leukoplastbomber ("Elastoplast bomber") or even more derisively as the "adhesive tape bomber," were somewhat unfair. The Me 323 was something of a sitting duck, being so slow and large an aircraft. However, no transport aircraft can ever be expected to survive without air superiority or at least, comprehensive local air cover, and it is believed that no Me 323s survived in service beyond summer 1944.
A total of 213 Me 323s were built before production ceased in April 1944. There were several production versions, beginning with the D-1. Later D- and E- versions differed in the choice of power plant and in defensive armament, with improvements in structural strength, total cargo load and fuel capacity also being implemented. Nonetheless, the Me 323 remained significantly underpowered. There was a proposal to install six BMW 801 radials, but this never came to pass. The Me 323 was also a short-range aircraft, with a typical range (loaded) of 1,000–1,200 km. Despite this, the limited numbers of Me 323s in service were an invaluable asset to the Germans, and saw intensive use.