A subsidiary of arms manufacturer BAE Systems has been fined £80,000 after a worker’s leg bone was shattered while test firing a gun on a Northumberland range.

The employee, from Hexham, was seriously injured in April 2008 when a metal bolt weighing seven kilograms ejected from the back of the gun into his left leg.

He spent six weeks in hospital and his injured leg is now 2cm shorter than his right.

The incident was investigated by the Health and Safety Executive (HSE), which prosecuted BAE Global Combat Systems Munitions Ltd for safety failings.

Newcastle Crown Court heard that a boresight aiming device had been left in the barrel of the medium-calibre gun when it should have been removed before firing.

When the gun was fired a build up of gas hurled the boresight into the worker’s leg, shattering it.

The firm, based at Farnborough in Hampshire, was fined £80,000 and ordered to pay £100,000 costs on Friday after pleading guilty to breaching safety regulations.

“This is a highly specialised global company whose safety standards should be industry-leading,” said HSE inspector Philip Smith.

“There were recognised preventative measures that should have been employed to make sure this kind of serious incident could not happen.

“As a result of their safety failure, a worker suffered a terrible injury.

“This incident emphasises the need for management to ensure preventative measures are effectively implemented on all equipment used at work.”