For the smaller bores button rifling may be a good way to go.
Unless there is an anneal, in a controlled atmosphere furnace, done after buttoning profiling will result in variations in bore dimensions. I.E. the bores will get larger at the muzzle. A swamped barrel would be bigger in the middle.
Buttoning does not work well in rifling more than what is used in PP or "naked" bullet guns or more modern stuff.
The stresses it sets up in the steel are extreme even at .004 deep rifling.
I used to work in place that button rifled barrels. Sure they still do.
IMO button rifling is not a good way to go for any serious barrel. And I have used quite a number of them over the years. There are many highly accurate brass suppository barrels that are buttoned. But they are stress relieved after buttoning.
Do you remember the problems with the shallow groove TC "Hawken" barrels that were button rifled?