CBTO Measurement

[PopCharlie]

I use a Sinclair comparator (the one with the interchangeable inserts) attached to my digital micrometer top jaw. I set the loaded round on the bottom jaw and slowly close the jaws until the insert stops on the bullet ogive. I wiggle the round a little to make sure its not tilted. The issue I have is that sometimes the insert will bite into the jacket. This will change the CBTO measurement by a few thousandths. Sounds like a simple process, but if you want to be precise, it is an issue. What tools/ techniques are folks using to get consistent measurements?

 

[dgeesaman]

I don’t think I would use a comparator that marks my bullets.

Are you able to get consistent measurements using less pressure?

If not I’d wrap fine sandpaper around a bullet and deburr the comparator. If that doesn’t help I’d junk it.

 

[Metal God]

The issue with the Sinclair inserts is that they are very close to the diameter of the bullet itself so the bullet tends to lodge into the insert . Yes they leave a noticeable mark by eye but I don’t feel they make a scratch or indentation of any type that would hinder the flight of the projectile .

I have found that I actually need them to slide in and kind of lock in to get a consistent measurement If they don’t lock in to the insert my measurements are often inconsistent so I figured they were designed to do so . I never really put much more thought to it than that .

With my fat fingers it makes measuring .224 bullets alone almost impossible ,

 

[PopCharlie]

I don’t think I would use a comparator that marks my bullets.

Are you able to get consistent measurements using less pressure?

If not I’d wrap fine sandpaper around a bullet and deburr the comparator. If that doesn’t help I’d junk it.

Dgeesaman,
I try to be very careful so I don't score the bullet. I use light pressure, but checking 50 rounds becomes a tedious chore with inconsistent results. So, I'm looking for a better method.
I like your idea of debuting the insert. I'll give that a try.
Thanks.

 

[justpassinthru]

I'm using the one made by Whidden Gunworks along with his bushings and have never experienced what you describe.

 

[PopCharlie]

I'm using the one made by Whidden Gunworks along with his bushings and have never experienced what you describe.

Hmmm....ill check it out
Thanks

 

[mike06]

This is what I use it is a 3-1 tool a bit more expensive but it is precise. You can buy it without the dial indicator.
https://www.redding-reloading.com/o...ant-indicator-headspace-and-bullet-comparator

 

[DaveTooley]

I use Whidden multi purpose over all length gage. I then grind a bushing till I remove the radius. Leaving a sharp edge. At -.001" under nominal bullet diameter I can easily verify any throat design and talk intelligently to any reamer manufacture about what is wrong. Does it leave a mark. Sometimes but means nothing in the wind.

 

[PopCharlie]

I use Whidden multi purpose over all length gage. I then grind a bushing till I remove the radius. Leaving a sharp edge. At -.001" under nominal bullet diameter I can easily verify any throat design and talk intelligently to any reamer manufacture about what is wrong. Does it leave a mark. Sometimes but means nothing in the wind.

I just ordered the Whidden tool and some bushings for my 3 custom rifles. I won't be able to grind them down, but it will get me started.
Thanks for the reply!

 

[Willie]

I use a sorting stand, Tubb comparator on base, and a .001 dial with a flat tip. The spring loaded stem puts the same pressure on each bullet. Much faster than calipers and more accurate, I believe, because pressure is consistent.

 

[Mikemci]

I like the Sinclair, for the same reason that you don't. Bullet fits the comparator hole much better than the one Hornady makes. Much less twisting and fiddling to get a precise measurement.

 

[WIB3]

I use a Hoover meplat trimmer. You can measure your Bullets and also your seating depth. If your pointing Bullets it also works wonderfully for trimming.

 

[Martin52]

The comparator here is very well made:

https://greensrifles.com/pics