BBTO or bearing surface?

[kvd]

One thing is certain - whatever a bullet looks like and measures while holding it, it will not look and measure the same as it comes out of the barrel. It will be mashed and most likely elongated to conform to the lands and groves of the barrel and have some degree of copper jacket stripped off. For this reason, measuring bullet for me takes the form of finding big outliers and the only important measurement to me is the point on the ogive that is the same diameter as the lands and the distance of this point to or into the lands.

 

[David Christian]

BBTO is all I do, although I'm in search of a better tool to accomplish the task over a Hornday comparator.

Here is the tool you need to measure bbto. Works great and is very fast!

 

[stifffingers]

Where is the most “bang” for your time sorting by bullet base to o-give or bearing surface for BR accuracy?
I have sorted some Berger 108’s by bearing surface using two hornady comparators but I can still see difference in them when comparing base to ogive.

Be careful, if you don't mark the two comparators and get them mixed up, all your loading data won't work. Test them bto only on the same loaded round and you will probably get a different reading.

 

[JimSC]

it isn't like a comaparator has a lot of moving parts or any sensitive adjustments. The only error possible is operator error or a malfunction in the measuring device. The diameter of the hole in the metal will not change if you measure the same bullet three times and get three different reading either the calipers or the operator is to blame

 

[dcali]

I think the difficulty lies in the alignment, and also the radius on the comparator. Too much lets the bullet tip, and too sharp let’s it dig into the jacket. I don’t see the need for precision beyond what a typical Hornady tool will give you, but that’s just me.

 

[JimSC]

I don't know if this will help but I "spin" the bullet or case in the comparitor while gently squeezing the calipers jaws snug with the other hand with a light source behind the measuring tool, the bullet or case tends to center itself and you can try make sure the base is level with the caliper jaws. That is how I use a Hornady comparitor, I am sure it would work with others