.50 Vickers MK manual and / or tech data?

[Bruce_in_Oz]

Trying to help the owner of a "conical flash-hider" .

Hope to get photos soon, but it is described as 200mm long and with clearance for a "serious bullet"

Apparently there is also a "mandrel" to help tidying up dents in the cone.

My wild guess is .50 Vickers, as used in quad-mounts on Royal Navy vessels. Also used, apparently, by the LRDG in North Africa. but not with the heavy quad deck mount,

[browningautorifle]

Once he provides pics it'll be easy. Really hard to say without. Could be for a 20mm also.