HM Coastguard teams from Newbiggin and Blyth joined in the four-day operation alongside Northumbria Police at Newbiggin Beach.
It was sparked after a member of the public came across items of concern, with searches then carried out leading to the recovery of the large amount of ammunition.
With inquiries underway by police, no further details have been released by the emergency teams.
The North East has experienced high seas in the last week due to the winter storms and gales, with waves of around 10ft crashing against the Northumberland coast.
A spokesperson for the Coastguard teams said: “Alongside specialist police search teams, carried out a number of visual searches as well as fingertip searches to locate any other rounds on the beach.
"Over 10,000 different rounds were located.
“As this matter is still being investigated by the police, the team are unable to release any more information.
“Should you see or suspect anything or anyone in danger around the coast then dial 999 and ask for the Coastguard.”
Photos shared by the teams showed its officers digging in the sand alongside police officers and carrying out checks of the sand higher up towards the promenade, as well as on the shoreline.
Anyone with information which could help police with the investigation can call 101 or pass on information via the force’s website and its Tell Us Something page.