I have loaded for the 9.3X57 for almost 40 years. Tried several different powders, and the most efficient loads for me have been Ball C2 with magnum primers.
It is no trick at all to get well over 2300 fps with 285 gr bullets, longest case life, no loose primer pockets, and good accuracy.
Here's a link to the most experienced 9.3X57 loader I am aware of: http://forums.gunboards.com/showthread.php?645-Handloading-the-9-3x57&p=207227#post207227
He has done a lot of load development and experimenting, including loading .375 jacketed bullets that have been sized down to .366 for the '57. He was living in BC when he posted in 2007, and may still be there.
It will take a while to read all his posts, but it will be time very well spent. I would have been well-pleased to have had his information when I started loading for this round in the early 80s.
Ted
And from Loaddata.com
Warning!#Notes:#The rifle used was a Husqvarna Model 46 with a 24 1/4-inch barrel. Norma cases and Winchester WLR primers were used throughout. An Oehler M33 chronograph was set at 10 feet from the muzzle. Group size is an average of three, five-shot groups at 100 yards. (Handloader Issue #283 - April/May, 2013)
Be Alert: Publisher cannot be responsible for errors in published load data.
Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS) Favorite?
232 Norma Oryx Hodgdon H-322 39.5 1967
Remarks:#extreme spread (fps): 61; cartridge OAL (inches): 3.00
232 Norma Oryx Hodgdon H-322 42.5 2215
Remarks:#maximum load; extreme spread; 33; cartridge OAL (inches): 3.00
232 Norma Oryx IMR IMR-3031 45 2171
Remarks:#extreme spread (fps): 29; cartridge OAL (inches): 3.00
232 Norma Oryx IMR IMR-3031 47 2314
Remarks:#maximum load; extreme spread; 41; cartridge OAL (inches): 3.00
232 Norma Oryx IMR IMR-4895 46 2185
Remarks:#extreme spread (fps): 37; cartridge OAL (inches): 3.00
232 Norma Oryx IMR IMR-4895 48 2287
Remarks:#maximum load; extreme spread; 49; cartridge OAL (inches): 3.00
232 Norma Oryx IMR IMR-4064 46 2143
Remarks:#extreme spread (fps): 41; cartridge OAL (inches): 3.00
232 Norma Oryx IMR IMR-4064 48 2255
Remarks:#maximum load; extreme spread; 36; cartridge OAL (inches): 3.00
232 Norma Oryx Winchester W-748 50 2198
Remarks:#extreme spread (fps): 14; cartridge OAL (inches): 3.00
232 Norma Oryx Winchester W-748 54 2314
Remarks:#maximum load; extreme spread; 9; cartridge OAL (inches): 3.00
250 Nosler AccuBond IMR IMR-3031 41 1976
Remarks:#extreme spread (fps): 33; cartridge OAL (inches): 3.20
250 Nosler AccuBond IMR IMR-3031 43 2088
Remarks:#maximum load; extreme spread; 29; cartridge OAL (inches): 3.20
250 Nosler AccuBond IMR IMR-4895 42 1965
Remarks:#extreme spread (fps): 48; cartridge OAL (inches): 3.20
250 Nosler AccuBond IMR IMR-4895 44 2073
Remarks:#maximum load; extreme spread; 42; cartridge OAL (inches): 3.20
250 Nosler AccuBond IMR IMR-4064 42 1950
Remarks:#extreme spread (fps): 38; cartridge OAL (inches): 3.20
250 Nosler AccuBond IMR IMR-4064 44.5 2112
Remarks:#maximum load; extreme spread; 26; cartridge OAL (inches): 3.20
250 Nosler AccuBond Winchester W-748 46 2072
Remarks:#extreme spread (fps): 35; cartridge OAL (inches): 3.20
250 Nosler AccuBond Winchester W-748 48.5 2152
Remarks:#maximum load; extreme spread; 39; cartridge OAL (inches): 3.20
270 Speer Hot-Cor IMR IMR-3031 42 2003
Remarks:#extreme spread (fps): 39; cartridge OAL (inches): 3.06
270 Speer Hot-Cor IMR IMR-3031 44 2090
Remarks:#maximum load; extreme spread; 32; cartridge OAL (inches): 3.06
270 Speer Hot-Cor IMR IMR-4895 42 1865
Remarks:#extreme spread (fps): 26; cartridge OAL (inches): 3.06
270 Speer Hot-Cor IMR IMR-4895 44 2039
Remarks:#maximum load; extreme spread; 11; cartridge OAL (inches): 3.06
270 Speer Hot-Cor IMR IMR-4064 42 1841
Remarks:#extreme spread (fps): 36; cartridge OAL (inches): 3.06
270 Speer Hot-Cor IMR IMR-4064 45 2087
Remarks:#maximum load; extreme spread; 38; cartridge OAL (inches): 3.06
270 Speer Hot-Cor Winchester W-748 47 2036
Remarks:#extreme spread (fps): 19; cartridge OAL (inches): 3.06
270 Speer Hot-Cor Winchester W-748 49 2127
Remarks:#maximum load; extreme spread; 28; cartridge OAL (inches): 3.06
285 Prvi Partizan IMR IMR-3031 42 1921
Remarks:#extreme spread (fps): 32; cartridge OAL (inches): 3.07
285 Prvi Partizan IMR IMR-3031 43.5 2008
Remarks:#maximum load; extreme spread; 24; cartridge OAL (inches): 3.07
285 Prvi Partizan IMR IMR-4895 43 1930
Remarks:#extreme spread (fps): 29; cartridge OAL (inches): 3.07
285 Prvi Partizan IMR IMR-4895 44 2017
Remarks:#maximum load; extreme spread; 41; cartridge OAL (inches): 3.07
285 Prvi Partizan IMR IMR-4064 42 1825
Remarks:#extreme spread (fps): 33; cartridge OAL (inches): 3.07
285 Prvi Partizan IMR IMR-4064 45.5 2071
Remarks:#maximum load; extreme spread; 18; cartridge OAL (inches): 3.07
285 Prvi Partizan Winchester W-748 44 1832
Remarks:#extreme spread (fps): 20; cartridge OAL (inches): 3.07
285 Prvi Partizan Winchester W-748 47.5 2026
Remarks:#maximum load; extreme spread; 28; cartridge OAL (inches): 3.07
285 Norma Oryx IMR IMR-3031 42 1940
Remarks:#extreme spread (fps): 31; cartridge OAL (inches): 3.12
285 Norma Oryx IMR IMR-3031 43.5 2021
Remarks:#maximum load; extreme spread; 16; cartridge OAL (inches): 3.12
285 Norma Oryx IMR IMR-4895 42 1835
Remarks:#extreme spread (fps): 40; cartridge OAL (inches): 3.12
285 Norma Oryx IMR IMR-4895 43.5 2019
Remarks:#maximum load; extreme spread; 31; cartridge OAL (inches): 3.12
285 Norma Oryx IMR IMR-4064 43 1903
Remarks:#extreme spread (fps): 38; cartridge OAL (inches): 3.12
285 Norma Oryx IMR IMR-4064 45 2076
Remarks:#maximum load; extreme spread; 27; cartridge OAL (inches): 3.12
285 Norma Oryx Winchester W-748 45 1908
Remarks:#extreme spread (fps): 31; cartridge OAL (inches): 3.12
285 Norma Oryx Winchester W-748 47.5 2038
Remarks:#maximum load; extreme spread; 19; cartridge OAL (inches): 3.12
286 Hornady InterLock IMR IMR-3031 42 1945
Remarks:#extreme spread (fps): 30; cartridge OAL (inches): 3.17
286 Hornady InterLock IMR IMR-3031 43.5 2021
Remarks:#maximum load; extreme spread; 33; cartridge OAL (inches): 3.17
286 Hornady InterLock IMR IMR-4895 42.5 1932
Remarks:#extreme spread (fps): 26; cartridge OAL (inches): 3.17
286 Hornady InterLock IMR IMR-4895 44 2036
Remarks:#maximum load; extreme spread; 38; cartridge OAL (inches): 3.17
286 Hornady InterLock IMR IMR-4064 42 1901
Remarks:#extreme spread (fps): 23; cartridge OAL (inches): 3.17
286 Hornady InterLock IMR IMR-4064 45.5 2083
Remarks:#maximum load; extreme spread; 26; cartridge OAL (inches): 3.17
286 Hornady InterLock Winchester W-748 45.5 1956
Remarks:#extreme spread (fps): 11; cartridge OAL (inches): 3.17
286 Hornady InterLock Winchester W-748 47 2018
Remarks:#maximum load; extreme spread; 31; cartridge OAL (inches): 3.17
For those with a Husqvarna model 146
Warning!#Notes:#Test rifle was a Husqvarna Model 146 with 24 3/4-inch barrel. Loads developed in Norma 9.3x57 brass, using CCI-200, Remington 9 1/2 and RWS-LR primers. All loads should be reduced by 10 percent and worked up carefully. (Handloader Issue #125)
Be Alert: Publisher cannot be responsible for errors in published load data.
Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS)
232 Norma IMR IMR-3031 45 2,335
Remarks:#Barnes data
232 Norma IMR IMR-3031 48 2,485
Remarks:#maximum, but accurate
232 Norma Norma N-201 49 2,329
Remarks:#Norma data
232 Norma Norma N-201 53 2,435
Remarks:#warm, accurate
232 Norma Winchester W-748 54 2,450
Remarks:#most accurate
258 RWS Rottweil R-902 46 2,115
Remarks:#RWS data; R-prefix powders are Rottweil, not available in the U.S., and are shown for reference only. R-902 is close to Norma 201, W-748 and BL-C(2).
258 RWS Rottweil R-903 48 2,001
Remarks:#RWS data; R-prefix powders are Rottweil, not available in the U.S., and are shown for reference only. R-903 lies between H-335 and IMR-4064
270 Speer IMR IMR-4895 46 2,145
Remarks:#good hunting load
270 Speer IMR IMR-4895 47 2,205
Remarks:#maximum
270 Speer Winchester W-748 46 1,985
Remarks:#accurate, mild
270 Speer Winchester W-748 48 2,165
Remarks:#accurate, maximum
270 Speer IMR IMR-3031 42 2,110
Remarks:#fair
286 Norma IMR IMR-3031 40 2,000
Remarks:#Barnes data
286 Norma Norma N-201 44.6 2,067
Remarks:#Norma data, maximum
293 RWS Rottweil R-903 47 2,001
Remarks:#RWS data; R-prefix powders are Rottweil, not available in the U.S., and are shown for reference only. R-903 lies between H-335 and IMR-4064
Never had it on the chrony, but my best load has been
42 grain imr 4064
Speer 270 grain