The bullet which killed Constable Stephen Carroll was one of two shots fired at him as he sat in the driver's seat of his car after he and another officer were lured to the scene at Lismore Manor in Craigavon in March 2009.
The Belfast Crown Court trial of a former Sinn Fein councillor and a mother and son facing charges arising out of murder also heard that the gunman, armed with a suspected Romanian AK47 assault rifle, using ammunition manufactured in Yugoslavia in 1982, had fired from approximately 50 metres.
A forensic scientist also claimed that the gunman had fired the two shots, suggesting the rifle was on semi-automatic mode when fired from a footpath between a lamppost and the corner of the closest building, which was under construction at the time.
The assault rifle and 24 rounds of ammunition were found in a follow-up search, hidden under an oil tank at the rear of a house in nearby Pineview estate.
The forensic expert said that the rifle had a Romanian-type foregrip fitted under the barrel, and while serial numbers had been ground off from two sections, a third set of numbers was noted inside.
The expert said when test fired the weapon discharged bullets to the right and slightly forward of the firing position, something which he later used to "back extrapolate" to ascertain the location of the gunman when he opened fire.
The expert added that from the gunman's estimated position, the bullets had also been fired through two sets of metal mesh fencing between him and Constable Carroll's car.
Later under cross-examination, he agreed that if any of the bullets had struck the chain-linked fencing, it "could have deflected the flight of the bullet". However, the expert said he had examined the fencing and found no damage, and in his opinion "the bullet had passed through the fencing".
Earlier, he also accepted that because he'd found brown coloured debris in the rifle barrel, similar to dirt, soil or rust, this too could have affected the path of bullets.
Trial judge Lord Justice Girvan has already heard the evidence of over 100 witnesses.
However, because of further legal matters to be dealt with by another judge, the Diplock non-jury trial has been adjourned.
Ex-Sinn Fein councillor Brendan McConville (40) of Glenholme Avenue, Craigavon, and John Paul Wootton (20), of Collindale in Lurgan, who both deny Constable Carroll's murder, have been remanded back into custody.
Wootton's mother Sharon has been released on continuing bail on a charge of perverting justice.