Can you rechamber my NEF or TC Encore…?
The real question often should be can my 308 barrel be rechamber to 338-06? Or some 30-06 Ackley Improved etc.
First when you thinking about rechambering a barrel the bore diameter must be the same unless you are willing to rebore the barrel as well. Reboring is often thought of as a cheap alternative to a new barrel. It is usually less expensive but the best reason for a rebore is when you have a gun that has some intrinsic value, either a family gun, or maybe a fancy barrel that has a quarter rib, custom sights, octagon, etc, that would be expensive to duplicate. Such barrels make sense to rebore.
Back to plane old rechambering… Just look at it this way, you must pick a chamber that is larger than the original chamber, ideally, larger in diameter and at least a little longer. Sometimes the original neck diameter was on the large size and when you rechamber it leaves a small groove or mark in the neck area of the chamber. Normally this is not a problem for function, but it leaves marks on your brass and might hinder accuracy.
Ackley Improved cartridge do now work well for single shot rechambers unless your starting from a much smaller case, like a 22 Hornet to a 22-250 AI. Now if you working with rimmed cases then an Ackley design is fine in a single shot simply because the rim handles headspace. Rimless cases headspace on the shoulder and Ackley rimless cases are .004″ shorter than the factory counterpart.
Anyway, single shots make for a fun and cheap way to try new calibers. Give it a try.