Chapuis:

Waiting for Daryl to respond, here, but in the meantime,

The x66 SM splits the difference in velocity between the x62 and the x64, correct?

As such, when all 4 are loaded to the same pressures, the three longer rounds will always be able to drive identical bullets to faster speeds than the shorter x57.

Whether this is always an advantage over the x57 or not depends on the game and the ranges at which it is shot.

For woods and MOST hunting I suppose, I'm waiting for the buying public to discover light fast handling mediums again. Maybe I am wrong, but when shots are 200 or less and the game is deer/elk/moose or something like those, the mediums in the .35-.375 bracket based on .308, x57 and '06 cases have a lot going for them.

The wound channels I've traced caused by my x57 in deer, elk and bear shot at 25-225 yards or so are good and wide but without the lateral and peripheral, hydraulic, "explosive" trauma of the light highspeed calibers or even the fast mediums. Guys with a 9x57, .358, .35 Whelen, 9.3x62, 9.5x57 and .375'06 probably find the same, depending on bullets used of course.