Took the M-1910 to the range today with a few developmental loads for the chronograph. I used ADI's AR-2206 powder for this sequence, as it worked best in my near-identical .444/.375 Lee Enfield loads.

Starting light with 42gr and working up to 46gr, results were as follows:

42gr -> 1870 fps
44gr -> 1950 fps
45gr -> 2015 fps
46gr -> 2070 fps

Extreme spread was high at the lowest load, but tightened up nicely at the higher loads.
Obviously I still have a ways to go though. Factory MV is published as 2150 fps with the 270gr bullet, and in the full-length rifle barrel I was hoping for at least that figure. Pressure was still mild though, so a couple more grains of powder shouldn't hurt.
If it starts to look a bit stiff, I'll change to AR2208 (Varget), but that would be slower than necessary I believe.

BTW Daryl, AR2206 is very close to the H4895 you recommend, which is actually rebadged AR2206H. AR2206H is only 1% to 2% slower than AR2206. Also, I think AR2206 may no longer be manufactured by ADI, being completely replaced by AR2206H? Someone mentioned this recently. When my 4kg kegs run dry I will have to come to grips with this circumstance!

I have been reading the posts on the 9x57 and 9.3 x 57 and can now understand why it is such a well-respected hunting cartridge. I'm privelaged to join your ranks, gentlemen.

...and yes, peter, the rifle is indeed frisky but quite manageable with these loads so far. One of my friends has a 9.5 carbine, and that gets your attention!