I think there may be another view. I think the steel blank prior to being bored and machined was heat treated to a particular hardness and strength. That strength is better than the same steel in its annealed state. However that increased strength was still machinable. By converting to a soldering process instead of a brazing process Winchester was able to preserve that original treatment rather than reduce it further through a brazing process that further lowered its overall strength through additional heat.