Josh,
Here you go (a demo video) ..
http://bulletin.accurateshooter.com/2015/04/muzzle-threading-dont-remove-too-much-steel/The issue is that button rifled barrels compress the steel outward, so if you cut away metal too much (any hunting profile) the end of the barrel where you cut the thread bells out (expands)...
The video does a great job of validating this, I did it myself on my own lathe and when I got down below .2” of sidewall I really started to notice it, frankly I just wanted to see it for myself.
When I checked the pressure requirements for cartridges and side wall barrel steel most got down to .15” as safe... for those pressures, BUT cutting a thread takes that down another .03 or more.. so most guys won’t thread a barrel under .7” , and a lot of field sporter rifles have .63” or so muzzles. On a 06... .63 - .30 = .33 for side all = .165” .... you get it.
Anyway - cut rifled barrels don’t do this because they don’t have that internal stress from button riffling...
It can be fixed so it doesn’t impact your groups if you did it to a button rifled barrel but you have to remove the lose rifling on a lathe to do so..
Regards,
Spot