For the M1910, start with round nose 270 grain and build them precisely like this;

Otherwise, expect to load only two cartridges at a time into your rifle. As covered in previous posts (on other threads), the early Schönauer magazines can be rather particular as to what they're fed. If the bullet profile is not right or set to proper depth, loading the third cartridge will likely cause a jam as the first becomes misaligned and stuck.

With cartridges built to the original profile, however, one can load from five round strippers (most 8mm Mauser clips work fine) with a slight push of the thumb and the magazine will function flawlessly. I'd highly recommend building at least five rounds exactly as shown in the Eley drawing (even if powderless and primerless 'dummies') just for the sheer joy of experiencing how beautifully that magazine does work when properly fed. That will give you the baseline from which to craft your loads - perfection.

As the pre M1924 magazines have no 'guide ring', any variation from original bullet profile and overall dimensions may cause binding of the cartridges in the magazine. If you use shorter or differently shaped projectiles, expect to experiment with such until you find profiles and seating depths that will function in your magazine. It's necessary that there be sufficient bearing surface where the projectile rides along the milled area at the lower magazine body.

If your projectile is not wide enough or set out long enough to engage the machined area at left, it may be prone to misalignment and jamming.

These work:

The (now nearly extinct) Hornady 3715
I believe the Woodleigh 270RN is dimensionally identical.

If you can have projectiles (decorative paperweights?) shipped to you from the U.S., check on these every now and again. I laid in a supply when they had some at .26 each in lots of 100 (click link): Midway

Detail of Eley drawing:

Original DWM 531: