Here is one of those G.Gibbs Mannlicher-Schoenauers, put together by them in 1905. I always thought that these rifles left the Gibbs shop as takedowns. Gibbs used the front action screw to lock in the full-thread barrel. All Gibbs rifles I have seen have a foreend cut at right angles.

I do not believe the slanted cut on the WW2-period M-S could serve the same purpose.