The requirements for a new gun would be:
- High mobility.
- High momentary rate of fire.
The FH77 was the first field howitzer featuring an APU to make it self-propelled for tactical movement.
The rate of fire was, at the time, exceptionally high for a 155 mm howitzer. The FH77 could fire 3 rounds in 8 seconds, or 6 rounds in 25 seconds. In a sustained firing role it could fire 6 rounds every second minute for 20 minutes.
FH77BThough the haub 77 was a formidable gun it seemed impossible to export. There were two reason for this:
The maximum elevation was limited to 50°.
It did not use NATO ammunition.
Therefore Bofors developed a new version - the FH 77B. The main difference was that the B-model used a servo operated interrupted screw breech, instead of the sliding block action on the FH 77. The maximum elevation had been increased from 50° to 70°. The barrel is slightly longer, 39 calibres, and uses a single baffle muzzle brake as opposed to the pepper-pot style muzzle brake on the 77. The engine was a Mercedes diesel. Since the B-version used bagged charges it was somewhat slower than the original model - 3 rounds in 10 seconds compared to 3 rounds in less than 8 seconds. The maximum range, on the other hand, was increased to 24km and using base-bleed extended to 28km.
Nigeria bought 48 pieces in 1980 and in March 1986 India ordered 410 of the Bofors FH 77B. The Indian also got a contract option for additionally 1,100 howitzers.
Soon after the $1.4 billion contract with India had been signed two Swedish left-wing journalists reviled that Bofors had paid kickbacks to Indian public servants. As a result of this India declined to exercise their option on the second batch. A decision India has had all reasons to regret, as the FH 77B proved it self to be accurate, reliable and durable.
Bofors, who had been self-assured enough to start the production of the second batch, found them self with some 50 howitzers but no buyer. The Swedish government stepped in and forced the Army to purchase 51 of the B-model.