Alan Hepper, an MOD engineer, was giving evidence at the inquest into the death of 11-year-old Francis Rowntree.
He said there was limited testing on rubber baton rounds before their introduction in July 1970.
Francis, known as Frank by his family, was shot by a soldier with a rubber bullet in west Belfast in April 1972.
He died in hospital two days later.
That same year, accident and emergency doctors at Belfast's Royal Victoria Hospital had wanted to publish their findings in the British Journal of Surgery, but were told by a scientific adviser to the Ministry of Defence that it would not be in the public interest.
The information pointed out that 80% of inpatients hit by the rounds had injuries to their head and neck.  It also suggested that Frank Rowntree had been hit from two to three yards.
'Tumbled in the air'
It suggested that soldiers must be made aware of the consequences of using  the weapon, that it could kill, blind, or seriously injure some organs.
The tests on potential wounding by the baton rounds had been carried out at the Defence, Science and Technological Laboratory, Porton Down, Wiltshire, by firing them in controlled circumstances at sheep.
The court heard also that tests showed that the batons tumbled in the air and often hit their targets side-on, although they could also hit end on, causing rather more injury or damage.
Mr Hepper, who works at Porton Down, agreed with a barrister for the Rowntree family that the chances of a target being struck end-on increased if a round was fired within 5-6 metres.
It is thought that Frank Rowntree was struck from close range.
Mr Hepper told the inquest that the effect and accuracy of the rubber baton round was tested more after its initial introduction.
'Far too dangerous'
He also said that the amount of gunpowder used was increased twice in a bid to make it more accurate.
A wooden baton round had been tested but quickly deemed to be far "too dangerous" and was never used operationally here.
The rubber baton round was then developed at the request of Army HQ in Northern Ireland to provide an option between small-arms fire and the use of CS gas.
The kind most commonly used by the Army in April 1972 was 15cm long, and fired with 55 grains of gunpowder at a speed of about 160mph.
Mr Hepper showed the court some of the weapons that might have been used to fire such a round during a riot.
The court heard it was most likely that a weapon called a "federal riot gun" would have been used by the Royal Anglian Regiment in April 1972.
At one stage, the weapon was brought to the front of the courtroom for the coroner to see, and then closely examined and handled by barristers and members of the Rowntree family, including Jim Rowntree, the brother of Frank.
It later emerged during cross-examination that in 1971 there were 16,752 baton rounds fired, and in 1972 there were 23,363.
The rounds were designed to simulate a hard blow with a fist or a rigorous blow by a baton, but able to be caused by a soldier from a distance.
It was recognised in the scientific papers at the time that the targets in Northern Ireland would most likely be teenagers and young adults.
By December 1972, Army documents acknowledged that very serious injuries could be caused when rubber baton rounds struck the head or face.
It emerged that an independent report compiled in 1982 observed that some rounds had been tampered with by soldiers in the past, with batteries or coins added to the case with part of the rubber round removed.
There have been allegations that Frank Rowntree was struck with a battery.
Mr Hepper agreed that whilst the testing of the baton rounds followed scientific principles, it was limited, hurried and piecemeal before the initial deployment of the weapon in July 1970.
An inquest has heard that information about serious injuries caused by rubber baton rounds fired by the Army was not made public in the early 1970s.