More than 200 weapons belonging to the British military have been lost or stolen during the past nine years, the BBC has learned.
The SA80 is capable of firing hundreds of rounds per minute
Some of the missing weapons are antique or obsolete, but more than half are handguns or assault rifles.
The Army says it has recovered about one in four of those lost.
The figures come after a soldier from Birmingham was on Monday jailed for seven years and four months for handling a stolen SA80 assault rifle.
Between 1997 and 2005, the Army has had 36 SA80 rifles go missing. Only 10 have been recovered.
The figure for handguns is higher, with 39 lost and seven accounted for.
Across the Army, RAF and the Navy, 123 of the two weapons type have disappeared, the majority stolen.
It is not known how many of those have been recovered.
An investigation by BBC News reporter Angus Crawford found gun control experts were concerned about any increase in the number of firearms potentially available to criminals.
The Ministry of Defence said all weapons were kept in secure stores and any incidents were fully investigated by the police and could be subject to a further internal inquiry.
In a statement, it said: "All Armed Forces personnel are given clear direction that weapons should never be left unattended or in the care of unauthorised people.
"When not in use they are always kept in secure stores.
"Only those who have a direct need are permitted access, and they are subject to security vetting."
On Monday, L/Cpl James Piotrowski was jailed by a court martial for handling a stolen SA80.
He pleaded guilty to possessing and handling it after another soldier stole it from Wellington barracks in London in 2004.
L/Cpl Piotrowski served for three months in Iraq with the Irish Guards.
The hearing was told another SA80 taken at the same time is still missing.