According to Jeremy Bamber there were three .22 rifles at the farm; an auto, a bolt action and an air rifle. There were also four or five shotguns; one a .410 single barrelled shot gun.
According to witnesses Nevill Bamber was very careful to ensure the guns were stored safely at all times. To store a gun safely it must be locked in a gun cabinet and ammunition should be stored in a separate lockable container.
The guns at the farm were not stored safely as police officer DI Cook noted. There was a cupboard, he said, where the family sometimes kept guns, but the only gun in it was a broken shotgun, a cardboard box containing ammunition, and various other items including a poker and a dartboard.
It was David Boutflower who removed the guns from the house. Two 12 bore shotguns were in the downstairs shower room and on the stairs leading up from the kitchen he found the air rifle and the .410 shotgun. In the cupboard in the den he found Nevill's 12 bore shotgun in a brown case.
Assuming that the police took the murder weapon there seems to have been another 22 rifle missing; the bolt action one, unless Jeremy had misremembered.
So DI Jones failed to see a shotgun case complete with gun and various other cardboard boxes, two of which contained silencers.
[All from CAL's book]