British soldiers in Afghanistan had to borrow ammunition from other Nato forces because of faulty rounds, the Ministry of Defence (MoD) has said.
3 Para saw heavy fighting in Afghanistan's Helmand province
Troops from 3 Para were lent rounds by American and Canadian forces for a month while fighting the Taleban.
The MoD said the issue came to light three months ago, and the faulty rounds had since been replaced.
The problem was highlighted after members of 3 Para posted a video on the YouTube sharing site.
According to reports in the Daily Telegraph, the soldiers refused to go on patrols until the ammunition was replaced.
The MoD could not confirm this.
While the MoD accepts there were problems with the .50 calibre rounds used in the Browning machine gun, a spokesman said there was "no problem" in borrowing supplies from allied units.
The spokesman added: "At present there are no problems with .50 ammunition or any other kind of rounds used in theatre."
In the video posted on YouTube, two soldiers are seen operating a Browning machine gun from a sand-bagged bunker.
The soldier operating the weapon is seen to have to re-cock it several times, sometimes being able to fire only a single round at a time.
But the MoD said it would be "inconclusive" to draw any inferences from the scenes shown in the video.
"Southern Afghanistan has extremely hot and dusty conditions which can sometimes interfere with the moving parts in a weapon. It would be misleading to blame this on defective ammunition", the spokesman said.