For what it's worth, the 'twisted' tube was a design feature of these rifles that allowed the use of pointed (Spitzer) bullets in a tubular magazine - the spiral kept the point of the following cartridge from touching the primer of the cartridge in front. Interesting inovation or what?

So, TrapperP, how long were you a Navy Fire Controlman?
Regards,
HockeyPuck
FCCM, USN, Ret.