Originally Posted by
6x47
There are two issues around this.
The first one as Tim mentions is that wall thickness becomes marginal with a half inch thread. This probably isn't a huge safety issue as muzzle exit pressure is way down on peak pressure but it's not clever to run anything close to the edge.
The other issue is a potential accuracy one, especially with button rifled barrels. Swaging the rifling into a barrel leaves (outward directed) stress in the area around the bore and if you cut away too much of the surrounding diameter, there is the definite risk the bore dimensions will grow at the muzzle. A belled outlet will never be helpful for accuracy.