bore guage

Yes, they are quite accurate if you have the right touch. You start with the gauge set slightly too wide for they bore at an angle with slight tension on the friction lock. As you sweep the gauge through center it will compress to the smallest diameter which is dead square with the bore. then tighten the friction lock and measure with a micrometer. You will also need a 3-4" or 4-5" micrometer to measure the snap gauge once it's out of the bore obviously. For that money just get one of these https://www.amazon.com/dp/B000J4K016/?tag=fabo03-20