Kgl. Kais. would probably translate to Imperial and Royal because the Austrian Kaiser Joseph was King (Koenig), of Hungary and Emperor (Kaiser) of Austria. Hofbuchsenmacher means gunmaker to the royal court.

St. m. G means Stahl Mantel Geschoss or steel jacketed bullet. 17,6 grams corresponds to 270 grains +/- which is the standard bullet of a 9,5x57 M.-Sch. If it is a 9,5x57, try the new Nosler 260 Accubond. If it feeds OK, it should be very accurate. It is in my M1910.

2.13 would be February of 1913. 865 might mean it was the 865th proof of that month. Normally Mannlichers have a V for Vienna next to the N which makes me wonder if this was proofed in Germany.

9,2mm might well be the bore. Cerrosafe is surely the safe way to go next.

A very nice rifle.