There are a couple different names for this. Progressive twist, Bartlein calls it transitional twist etc... Basically, the twist rate changes from breech to muzzle. From what I understand, this was primarily designed for bullets with driving bands. However, there is a belief that there are other benefits such as reduced torque on the barrel. Which translates into being more able to watch bullet strikes if used in conjunction with a quality muzzle brake.

Does anyone here have a T- Style barrel? Benefits? Drawbacks? Thanks.