Bombardier's station, with windshield wiper and .50 caliber machine gun
The M2 .50 caliber is a peach of a weapon, developed by the legendary John Browning in 1921, it is still in service now. The bullet, weighing 2 ounces and measuring 1/2" (12.7 mm) across produces good effect against most thin-skinned targets. They tend to fire 600-1000 of the 6 inch long cartridges a minute. A B-26 like this probably distributed 10,000 rounds of ammunition among its dozen or so guns. If you look along the fuselage, there are 2 blisters on each side with a fixed .50 in each one (a total of 4) fired by the pilot. This was effective against trains and convoys, which the B-26 excelled at.