Later in 1941, the first Liberators entered RAF service. This model introduced self-sealing fuel tanks, a plug in the forward fuselage to create more space for crew members and, more vitally, ever more equipment such as ASV Mark II radar (anticipated early in the Liberator's development when Reuben Fleet told the engineering team he had a gut feeling the nose was too short). The Mark II was the first Liberator to be equipped with powered turrets, one plane having them installed before leaving San Diego, the remainder having them installed in the field: four Browning Boulton Paul A-type Mk IV with 600 rounds of .303 in the dorsal position; and a Boulton Paul E-type Mk II with 2200 rounds in the tail (later increased to 2500 rounds), supplemented by pairs of guns at the waist position, a single gun in the nose and another in the belly, for a total of fourteen guns. The maximum take off weight was slightly raised to 64,250 pounds, the maximum altitude lifted from 21,200 to 24,000 feet but the maximum speed was reduced to 263 mph, largely as a result of increased drag.