Aircraft gun sight?

[John H Turner]

I have this rear sight which I think may be from an aircraft machinegun. The reason I think this is because I was given it by someone who had been a civilian employee at an RAF station during WW2 and after. It looks a bit like the ones I have seen mounted on the Vickers K. It has what looks like 100 M.P.H. roughly scratched on one side and BSA in a circle on the base.
Can anyone identify it for me? I have had it for about 40 odd years now and always wondered what it came off.

Thanks,

John.Attachment 80670Attachment 80671Attachment 80672

Information

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[Flying10uk]

Are you able to give a few basic sizes/dimensions, please, which may be helpful to members and perhaps another close up picture of the rod part may help.

[Woodsy]

It appears to be the barrel-mounted rear anti-aircraft (and also aircraft use) sight off a Lewis gun. BSA made the Lewis guns in all their various styles. If you wish to sell it send me a PM!

[browningautorifle]

Very odd item to have fall into hand.

[Peter Laidler]

I probably have its brother........ I have the bead type ring-clamp foresight from a side mounted .50 Browning MG from a Flying Fortress. Recovered when the crashed remains were dug up in the Fens in the late 80's. Together with an old wartime dated brass 3d and pre-war copper 1d (old english coins) that I have inset into the little wood plinth the sight now sits on.

[mrclark303]

If we assume the sight is WW2 related (it could well be WW1, 20's or early 30's) my best guess would be the Vickers K sight for Fairey Battles the rear gunner. Post battle of France/Britain, the survivors, plus the remaining production run were pressed into second line duties, Base Cooperation flights, target tugs etc. The rear gun was removed from virtually all of them for re-use.

[CINDERS]

I have been trying to find a good picture of the ring sight in an early Hurricane fighter found one but could not enlarge it with clarity the ring sat where the reflector sight ended up and the bead was on top of the top engine cowling may have to look at one of my books to see if I can picture one from there it was also threaded on the bottom as per pic.

[John H Turner]

I have done a quick sketch showing the principle dimensions (in mm) although it would most certainly have been made to imperial measurements (I have been using metric for too long now). It is non magnetic and quite light at 25.4g. The RAF station that I mentioned was RAF Ternhill in Shropshire. As far as I can tell they did have Spitfires and Hurricanes early on in WW2 but then became a training base so I assume various second line aircraft appeared there. Does that help at all?

Thanks,

John.

[Woodsy]

After comparing John's drawing to the rear socket on my aircraft Lewis barrel I can confirm that it is the correct Lewis sight. It would be a perfect fit and the pin hole aligns.

[mrclark303]

Training base you say John, I'm sticking with the Fariey Battle rear gunners sight, many were used as trainers from late 1940 on