Not much load info on the interwbz but some interesting articles.
https://www.ballisticstudies.com/Knowledgebase/9.3x66+Sako.html
9.3x66 Sako
History
Released in 2003, the 9.3x66 was developed by the Finnish company Sako for their Model 75 rifle. With U.S cartridge designers inventing short fat cartridges for higher efficiency during the period of 2000-2003, designers of the 9.3x66 approached the design of the new medium bore cartridge from a different direction. The 9.3x66 case is simply the 9.3x62 case stretched to 66mm, the case has long base to shoulder dimensions with a relatively short neck. Sako marketed the 9.3x66 as having both superior ballistics and penetration than the .375 H&H Magnum in a small non belted case with superior handling and feeding qualities.
Performance
Unfortunately, Sako’s initial statements were somewhat optimistic and since this time, advertised speeds for factory loads have been heavily revised. This cartridge has the potential to produce velocities roughly halfway between the 9.3x62 and the 9.3x64 Brenneke. The 9.3x66 produces around 75fps higher velocity than the 9.3x62 and around 75fps lower velocity than the 9.3x64 Brenneke. The step up in power over the 9.3x62 will to many seem pointless, filling a gap that did not need filling.
Negatives aside, the 9.3x66 is a relatively powerful medium bore cartridge which can be put to use on a wide range of game. Those interested in the similar .30-06 case might also find this design somewhat interesting. If you have ever wondered what might happen if you could stretch an Ackley improvement further, this might be the result.
Factory ammunition
Sako produce three factory loads for the 9.3x66, these include the 15 gram (231gr) Speed Head (soft point) at 2510fps, the 18.5 gram (286gr) Hammerhead (core bonded) at 2490fps (down from an initially advertised velocity of 2540fps) and the 18.5 gram (286gr) Powerhead (Barnes TSX) at 2440fps (down from 2540fps).
These loads are fairly straight forwards in design, a light and soft load for light game along with heavy and tough loads for large heavy game. As can be seen, currently advertised speeds differ from when this cartridge was first launched.
Hand loading
Those who wish to hand load the 9.3x66 will need to source brass (or ammunition) from Sako. Dies are currently made by RCBS.
Suitable powders include medium burn rates such as Varget (ADI 2208).
Those who cannot find load data can easily use .35 Whelen load data with like weight bullets as a starting point.
For more information on 9.3 caliber bullet performance, please refer to the 9.3x62.
