Just some FYI...according to Ed Rayl, there are two considerations to over boring an existing barrel. One is the wall thickness but that's less important than the manufufcturer's type/size of breechplug threads that are used.
When the barrel boring operation takes place, the boring bit goes completely though the barrel end to end...it does not go in from the muzzle and stop short of the breechplug threads. So if the existing breechplug threads in the barrel are reduced too much, there won't be enough left for the plug itself to get a safe purchase on.
TC and GM's 1" barrels accept a .62cal smoothbore OK...and the barrel walls are still thick enough to even add .012" grooves to a .62cal smoothbore making it rifled, which Ed Rayl did on one of mine.