Loading the Mach IV now for a few years with $165 die set, don't see any advantage in running to the new 17 Fireball cartridge at all. Remington catalog shows a 1:9 twist for a 20 gr. pill, but regular 17 Rem. is a 1:10....so I don't know why they did that. r in s.

The slower the velocity of the bullet, the faster the rifling twist needed to properly stabilize the bullet. Since the 17 Remington has higher muzzle velocity, it can use a slightly slower twist.

I would imagine if the 17 Fireball takes off the 25 grain Vmax will come out in factory loads next. There have been reports of some 10 twist 17M4s not sabilizing that bullet so a 1:9 twist is needed.

Remington surely wanted to err on the side of caution rather than use a 10 twist that my not stabilize heavier bullets in the event they come around.

Chris