Aha, a clue on the Morane-Saulnier BBs from Davilla's French Aircraft of the First World War. While Morane-Saulnier never got production orders for the BB from the French they did sell a few to Russia; Spain built a few; and the UK received about eighty.
The Type BBs were usually armed with two 0.303-inch Lewis machine guns. One was fixed at an angle to the top wing to fire upward and was controlled by the pilot; the second gun was on a flexible mount in the observer's cockpit.
I take "upward" to mean "mostly forward, just over the propeller", but perhaps it could be raised to a higher angle as well, like the Foster mount on a SE5a? One picture shows it in a fully-forward angle (or nearly); another has it kind of upward and skewed, as if it's sort of loose in a reloading position.
I think the observer would be doing the reloads in any case.
Bookmarks