US - Martin Model 194

[ZakTheBuilder1]

Prototype Long-Ranged heavy bomber
The design rivaled the Boeing B29
Four engines, propellers behind the wings trailing edge, another thing was the contra rotating propellers for additional force,
Had remote controlled turrets with four 50cals and 2 37mm autocannons

Able to carry 20 to 30 thousand pounds including the fuselage space
Able to fly at over 350mph and for over 4,000 miles
Rate of climb is 1000 ft per minute.

Sadly it is only proposed...
Source is military factory. Com

The project started in 1942 and died in 45