You might want to consider loading that a bit hotter, since you're probably well under Mach 1 (~1126 fps @ standard conditions) before impact at 1000 yards. Unless your chronograph tells you otherwise, MV with that charge is probably a bit under 2400 fps, even with the long barrel. The strong 98 action should be happy to digest significantly higher pressure than your current load generates. QuickLOAD estimates follow -

Cartridge : 8 x 57 IS (8 mm Mauser CIP)
Bullet : .323, 200, Sierra HPBT MK 2415(2430)
Cartridge O.A.L. L6: 3.228 inch or 81.99 mm
Barrel Length : 29.0 inch or 736.6 mm
Powder : IMR 4064

Predicted data by increasing the given charge,
incremented in steps of 2.778% of nominal charge.

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

+00.0 86 42.30 2391 2538 37810 5459 97.6 1.630
+02.8 88 43.48 2448 2662 40600 5588 98.2 1.578
+05.6 90 44.65 2505 2787 43588 5707 98.8 1.529
+08.3 93 45.83 2561 2913 46787 5816 99.2 1.482
+11.1 95 47.00 2617 3042 50215 5914 99.6 1.437 ! Near Maximum !
+13.9 97 48.18 2672 3171 53889 6001 99.8 1.394 ! Near Maximum !

Tabular trajectory data at Std.ICAO Atmosphere
-------------------------------------------------------------------------------------
Gun / Ammunition : 8 x 57 IS (8 mm Mauser CIP)
Bullet : .323, 200, Sierra HPBT MK 2415(2430)
Bullet weight : 200 grains or 12.96 Grams
Muzzle velocity : 2391 fps
Ballistic Coefficient(s) (G1):
C1=0.511@V>2300 fps;
C2=0.496@V>1700 fps;
C3=0.453@V>0 fps;

-------------------------------------------------------------------------------------
Range Velocity
-------------------------------------------------------------------------------------
| 0 2391
| 1000 1083 (subsonic)
-------------------------------------------------------------------------------------

Gun / Ammunition : 8 x 57 IS (8 mm Mauser CIP)
Bullet : .323, 200, Sierra HPBT MK 2415(2430)
Bullet weight : 200 grains or 12.96 Grams
Muzzle velocity : 2672 fps
-------------------------------------------------------------------------------------
Range Velocity
-------------------------------------------------------------------------------------
| 0 2672
| 1000 1211 (supersonic)