81mm query - what were these used for?

[exat808]

I have just acquired 6 of these units. Each is a standard 81mm body fitted with a plug and tail unit. The tails all have fired primary cartridges fitted. Every body contains HE substitute. The bomb bodies are all painted deep bronze green overall with "INERT" stencilled in white on the ogive. There are no other stencilled markings.
Each bomb is fitted with the robust aluminium collar assembly which is tightly fitted over the body as shown. The collars have opposing screw and bolt assemblies as per the photographs.
I acquired the bombs directly from the company that manufactured them. The bombs came surprisingly from the aircraft and airweapons construction division of the organisation. There was a suggestion from the staff that they were used in trials for bomb release mechanisms but why not use conventional inert airdropped munitions?

Any ideas?

 

[highlandotter]

May be an atempt to utilise these from light planes, such as single engined prop planes?

 

[HAZORD]

What is the outer diameter of the aluminum sleeve? They could have been sabots to adapt them to 4.2 inch or 120mm.

 

[exat808]

What is the outer diameter of the aluminum sleeve? They could have been sabots to adapt them to 4.2 inch or 120mm.

A good thought but I would maybe disagree due to the presence of the screws and bolts through the collars and also due to the extremely tight fit of the collar around the bomb body which would prevent it being ejected in flight. The diameter of the collar is about 112mm. Other evidence against it being fired is that it was acquired from an aircraft and airweapons manufacturer not a land ordnance manufacturer.

 

[weberoed]

a WHILE BACK i WAS RESEARCHING A 81MM THAT WAS IN SOME KIND OF CONTAINER AND SPRING LOADED. WHILE LOOKING INTO IT I DISCOVERED A LOT OF INFORMATION ABOUT 4.2" MORTAR AND 105MM HE BEING USED AS AERIAL BOMBS FROM HELICOPTERS DURING VIETNAM. THEY JUST REPLACED THE NORMAL PD FUZE WITH A IMPACT AIRCRAT FUZE. NOT SAYING THIS IS THE SAME, BUT THE COMMENT ABOUT IT BEING IN BOMN RELEASE TESTS SOUNDED FAMILIAR.

ALSO THAT ALUMINIUM COLLAR WOULD GREATLY EFFECT THE FRAG PATTERN IF IT WERE USED ON AN HE 81MM