The "proper" way to measure throats/bore/whathaveyou;
Get dead soft, "pure" lead- I use fishing weights of close, but oversize diameter- and drive them through with a dowel and hammer.
You dial calipers, if reasonably accurate, should get you close enough.

or-

Pin guages

or- "Cerrosafe" casting.

An alternate and effective method is to simply use a jacketed bullet of known diameter; gonna be .429" or .430".
If they don't pass through throats with moderate hand pressure (most will JUST hang up and then require gentle hand pressure with a ballpoint or something- to drop through)- they are too tight.

Again- this is probably a non-issue if you shoot jacketed exclusively, and/or are comfortable with 2"/3" groups at 25 yds.
A lot depends on what game you're after and the associated accuracy requirement, and/or- how anal are you?

A guy once told me (regarding shooting performance under pressure)- "first, you gotta have confidence in your equipment".
I find that to be true for me.
If I KNOW the gun/ammo combination will hit a half dollar, every time, at 25 yds.- I merely have to concentrate on my shooting.