http://www.csd.uwo.ca/Elevon/baugher_us/a20-17.htmlThe A-20G was first ordered on June 1, 1942 and first delivered in February of 1943. It introduced a solid nose armed with four 20-mm M2 cannon with 60 rpg and two 0.50-inch machine guns with 350 rpg. The four cannon were grouped in the forward part of the nose and projected well forward of the nose, with the two machine guns further back in the lower part of the nose. This new nose was introduced as a result of combat experience in the Pacific, where glass-nosed A-20s had been fitted with field modifications to increase their forward firepower during low-level strafing missions. The new nose made the A-20G slightly longer than previous variants. The A-20G retained the 0.50-inch flexible machine gun with 500 rounds in the rear cockpit, as well as the 0.30-in or 0.50-inch tunnel gun. The dorsal gunner's position was no longer equipped with emergency flight controls, and provision for photographic equipment was also deleted. Heavier-gauge armor plate was used, adding some 400 pounds to the weight. Carburetor deicing equipment was added.
However, the 20-mm nose cannon had a slow rate of fire and were prone to jamming, and after 250 aircraft were completed, the four cannon were replaced by four 0.50-inch machine guns beginning with the A-20G-5-DO production block. Two more 0.50-inch machine guns were added in the lower portion of the nose, bringing the total number of forward-firing machine guns to six. Most of the cannon-armed A-20Gs were eventually turned over to the Soviet Union.-All above from site
60 rpg would be expended very fast. only 250 were built and they were very unreliable. The A-20 we have now is far better.
