Five centuries of searching for one of Britain's most significant battlefields has finally ended with the discovery of "extraordinary and unexpected" pieces of artillery in a Leicestershire field.

The finds near Market Bosworth at last pin down the notoriously "wandering site" of the battle that overthrew Richard III – the last English king to die at the head of an army – and established the Tudor dynasty and the modern state.

Surrounded by school parties still studying at least four wrong locations, a bevy of archaeologists unveiled 22 primitive pistol bullets and cannonballs, alongside soil surveys and data from metal detection over 2.7 square miles.

The revelations arise from an overlooked trough of rolling countryside two miles from the previously most widely accepted battlefield, below Ambion Hill.

The scale of the ammunition haul transforms the battle of Bosworth's significance from a national landmark (it is usually ranked with Hastings, Naseby and the Battle of Britain) to international importance.

Glenn Foard, who led the £1m three-year survey for the Battlefields Trust, said: "We are seeing here the origins of firepower which led to an empire spanning the globe. Now this needs to be explored on every battlefield of the period in Europe."

Pictures of stalwart yeomen with bows and arrows have been instantly outdated by the find, which shows how the battle, in 1485, was a change from previous encounters in the Wars of the Roses.

Foard said: "Only two bullets have been found in 27 years' work at Towton [Britain's bloodiest-ever battle, fought near Leeds in 1461]. We are sure that we will dig up plenty more here."

The lead used in the ammunition that was found, some of it mixed with pebbles and flints to save money, would be far less prone to rust than iron arrowheads.

The exact location of the site, between the villages of Dadlington, Shenton, Upton and Stoke Golding, will not be publicised until next year, when the survey ends. But the four villages have hotly disputed the issue for centuries, referring to post-mediaeval texts and place-name evidence, such as Crown Hill, renamed from Garbrodys Hill some time after 1485.

"Our discovery suggests that the Crown Hill story is probably right, that Henry VII placed the crown on his head there after one of his soldiers found it in a thorn bush. We will never know, but it would have been the obvious place," said Foard.

The artillery discovery occurred after nearly three years of false leads. There was one shock when the site of a marsh, mentioned by chroniclers as protecting Henry's flank, proved a dead end. Foard said: "We really thought we'd nailed it, but soil surveys showed that the marsh had dried up in Roman times. Thank goodness, we found another one."

The discovery ends a prolonged period of nerves at Leicestershire county council, whose Battlefield Centre, at Ambion Hill, includes reconstructed mediaeval houses and staff marching about in full armour with swords and pikes. "We're relieved and delighted that our battlefield hasn't gone wandering off into Warwickshire or the West Midlands," said Heather Broughton, director of community services. "OK, the centre [built in in 1974] isn't in exactly the right place, but we're planning a trail to overlook the real site which any ten-year-old 10-year-old will be able to manage from here."

The team's work was praised by English Heritage's regional inspector, Jon Humble, who said: "This is the second epic victory on Bosworth's history-steeped soil. It has taken more than 500 years to reveal one of Leicestershire's greatest and most elusive secrets, but this is a world-class example of what can be received through archaeological research."

Des Gallagher, of the Heritage Lottery Fund, which paid for the survey, called the results "groundbreaking stuff, altering our national history".

Axel Müller, director of the International Medieval Congress, which two years ago reconstructed early mediaeval cannon at Leeds University,said: "Scholars will be settling down from tomorrow to think about what this means for studies of firepower in the development of warfare."

The news absorbed visitors to the centre, including a party of teenagers from Soar college, Leicester, who set about trying to work out the location of the new site. Mark and Marianne Lester, a sales manager and civil servant from Hinckley, said: "We've been here before and we know quite a lot about the other battlefield sites. Now we'll have to start finding out about this one."

Meanwhile, the chair of the Battlefields Trust, Frank Baldwin, called for stronger protection of Britain's battlefields to deter treasure hunters. He said: "We face public spending cuts but these places are a potentially a huge revenue earner. Normandy alone has 10 times more battlefield centres than there are in the whole of the UK."

History lesson

King Richard III of England slept badly on the night of 21 August 1485 and so did his army commander, the Duke of Norfolk, who had received the anonymous message: "Jockey of Norfolk be not so bold, for Dickon thy master is bought and sold."

So it proved the following day when 10,000 loyal Englishmen were outwitted by an army half their size, mostly Welshmen and French mercenaries, ably commanded by the Earl of Oxford. For the last time in English history, a monarch died on the battlefield, after a last desperate appeal for a horse. So the chroniclers have it, but details of the engagement will be altered by today's finds. What is undoubted is that Bosworth was one of Britain's most important battles, ending and beginning an era.

As history stands now, Richard drew up his force on Ambion Hill, near Market Bosworth, Leicestershire, and bombarded the invading force of Henry Tudor (soon to be King Henry VII). It was a rash order to charge which undid Richard. The king almost reached Henry but the vacillating Lord Stanley, whose 6,000 men had stayed neutral, entered the battle on Henry's side.