A tank explosion which killed two British Army soldiers was caused by a design flaw, a coroner has found.
Royal Tank Regiment corporals Matthew Hatfield, 27, and Darren Neilson, 31, died during a live firing exercise at Castlemartin Range in Pembrokeshire.
A seal stopping explosive gases escaping into a tank crew's turret was not in place before the lethal blast.
The widow of one of those killed said "lessons must be learned from the deadly incident".
Cpl Neilson, 31, from Preston, Lancashire, was the tank commander and was thrown from the turret in the blast on 14 June 2017.
Cpl Hatfield, 27, and a father of one, from Amesbury, Wiltshire, was loading ammunition.
Both men were taken to hospital but died of their injuries the following day.
Two other soldiers, Warrant Officer Stuart Lawson and Trooper Michael Warren, were also injured but survived.
The airtight seal, a bolt vent axial (BVA), that would have prevented explosive gases being released into the tank's turret was not in place when the men fired on 14 June 2017.
Senior coroner for Birmingham and Solihull Louise Hunt said the "hazard" had not been adequately tested by the gun designers or the Ministry of Defence (MoD) in manufacture.
The tank chassis and turret is built by BAE Systems, while the gun itself was made by Royal Ordnance.
There was no written process to check the presence of the airtight seal and the soldiers were unaware it had been removed on a prior exercise.
Ms Hunt said: "The main cause of this incident was the tank being able to fire without the BVA assembly being present.
"During production and manufacture of the gun, this hazard was not adequately considered or investigated and therefore the ability of the gun to fire without the BVA present went undetected."
The inquest also revealed that a second blast in the tank was caused when incorrectly stowed ammunition bags exploded during the incident.
The coroner heard a succession of troopers give evidence that the charges were sometimes stored out of heat-proof storage bins within the turret, including an occasion where one was "on a soldier's lap".
After the inquest, Cpl Neilson's widow, Jemma Neilson, said health and safety should have been "world class" and called for immediate changes by the MoD and Army.
She said: "No soldier should ever be killed in training.
"Lessons must be learned, cultures must change and the MoD must accept failings and implement change immediately.
"An incident of this nature must never happen again."
The coroner has sent a report to the MoD and the gun designers to prevent future deaths.
The Army said it had already improved training, weapons drills, and procedures.