Best method for measuring distance to lands?

[expiper]

How many shots does your rifle advance the bullet contact to the throat .001" down the barrel?

Bart,,,I have found most of my 6mm's (BR's-Dashers) wear the throat ~.002"-.003" per hundred rounds,,,naturally this varies with charge wt.(which varies with bullet size) and powder type and whether the bbl is cut or buttoned,,,Roger

 

[Bart B.]

My 308 Win barrels eroded throats about 30 to 40 rounds per .001 inch.

30-338 barrels about 12 to 15 rounds per thousandth.

264 win mag about 6 rounds.

Remember bottle neck case shoulders are the reference for bullet jump. They're against chamber shoulders when fired. Case heads are a couple to several thousandths off the bolt face when fired

 

[Bart B.]

The several 7.62 arsenal barrels in Garands I wore out had about the same throat erosion rate.

Throat erosion gauges went in about .100" further every 1000 rounds. They taper in diameter .010" per inch from .2990" at front tip to .3090" at the back of the gauge head.