45-70 Barrel Dimensions for Paper Patching

[Lumpy Grits]

Most 'peters' have bit of choke at the muzzle.
Those hole gauges only tell you the size at the point you measure. As a machinist for over 40 years I'll tell you that I don't like them.
You'll get a much better 'read' with a camber cast that includes the bbl throat/leade.
Or-You could also drive a lead ball from the breech to the muzzle and measure that.
Gary