Hi
Perhaps the following for consideration:

There exisited no set in stone dims. for the 45 colt cart. for many, many years.
What dims. would a manufacturer use for chambering reamers? The largest size they could possibly get away with.

I was always taught that colt used the same rifling tools for all 22 and 22Magnums, due solely to cost.
That maybe why the 22 mag colts never shot good for me.
I have had ruger blachawks with throats that would swallow 458 winchester mag. slugs

My employer for the last 34 years always orders the largest dia. drill or reamer that fits the size spec so that when the tool is resharpened and comes back to me slightly smaller it still fits the spec.
If anyone here thinks smith colt ruger etc. would order a reamer on the small side of the spec. they would all be out of bussiness in 6 months or less
HTH
Don