Congratulations on your acquisition.

I, too, have a Mannlicher Schoenauer M1910 factory Take Down. It was my Grandfather's previously. She's a joy to load for and shoot.

The +.05 on your receiver and -.05 on barrel are assembly marks to ensure proper chamber length (mine has +.15 -.15).

The .375 EX. 43 Cordite 270g MAX (mine has same) indicates a recommended diet of .375 Express (.375 Nitro Express Rimless) filled with 43 grains of Cordite and a bullet weighing a maximum 270 grains.

For brass, try fresh .35 Whelen. I have used that with Hornady 3715 (270 grain Round Nose) and a set of RCBS dies to make exact dimensional duplicates of the original DWM 531. Cut the .35s to the proper length after running them through the FL die.

Otto Schoenauer's magazine is a lovely bit of kit, but is rather particular as to what it's fed.

The magazine is machined to accept the exact length, shape, and profile of the proprietary MS cartridge for the specific model. For the 1910, that was DWM 531. Make your reloads to the exact dimensions of DWM 531 for a smooth, effortless feed. Seat the RN projectiles to the exact proper depth (right at the cannelure with Hornady 3715). Use of spire point or other shapes or lengths of bullet may allow the cartridges to shift and bind within the magazine.

I and others have posted a lot of information and photos to thefirearmsforum.com regarding Mannlicher Schoenauers.

I can't seem to get photos or scans to load to this one.