Four staff at green consultancy Carbon Managers were setting off for a tree-planting trip in Scotland from Bristol Airport on Wednesday when one of their number was singled out for a search.
Account manager George Thomas, 19, had toothpaste and aftershave taken by the security guard but only realised when he reached Inverness that a handful of undetected live rounds were in his coat.
Geremy Thomas, director of the company which helps businesses become carbon neutral, said he could not believe the "lax" security had picked out his son's toothpaste but overlooked the live cartridges.
The airport said it had no record of the incident having taken place, but confirmed that ammunition was not allowed on board.
Mr Thomas, 48, from Frome, said: "The Carbon Managers team set off for Inverness from Bristol airport as we were heading up to the Alladale wilderness Reserve on a two-day tree-planting trip.
"The four of us flew with easyJet and only had hand luggage. We went through the scanner and my son George was pulled aside. His toothpaste and after shave were captured by the security guard.
"Once we arrived at Alladale, we opened our hand luggage in preparation for our first day's tree planting. George put his hand in his coat pocket and realised he'd inadvertently carried a handful of shot gun cartridges from a past day's shooting onto the plane.
"They were left over from a clay pigeon shoot. That was a mistake on his part and he'll learn from that. None of us could believe that they'd confiscated his toiletries but completely missed live ammunition.
"I find it worrying that security is so lax and that there are such bizarre double standards."
A Bristol Airport spokeswoman said: "Bristol International Airport is not aware of this alleged incident but can confirm that the airport is fully compliant with all DFT screening regulations. No ammunition is allowed on board a plane."