I've been testing my new Sinclair concentricity gauge and seem to have run into some problems with it. I have an older Bonanza concentricity gauge that I've been using to check it against. Pics below of both, with a dummy 6 PPC round on each:
The problem I'm having with the Sinclair model is in keeping the round properly positioned as I rotate the round on the tool. I've set the dial gauge pointer to have only light pressure on the bullet so as not to tip the round, but even with that and trying to hold the round down on the ball bearings--and back against the stop--I'm having trouble controlling the process.
With the Bonanza tool, the round is held fairly tightly fore and aft by the spring-loaded plunger stop on the head of the case. The V-holder for the bullet allows one to hold the round down the same amount each time when set up properly. It is much easier to use than the Sinclair.
I'm getting very different runout readings from the two tools. On the Bonanza, it is showing about .0015" runout, whereas on the Sinclair, I'm getting more like .006". However, this latter may be more due to my problems discussed above than any actual runout in the round. Just FWIW, the case is an unfired, neck-turned Norma case, with a Bart's 68-gr. 6mm. bullet.
Any thoughts on this?


The problem I'm having with the Sinclair model is in keeping the round properly positioned as I rotate the round on the tool. I've set the dial gauge pointer to have only light pressure on the bullet so as not to tip the round, but even with that and trying to hold the round down on the ball bearings--and back against the stop--I'm having trouble controlling the process.
With the Bonanza tool, the round is held fairly tightly fore and aft by the spring-loaded plunger stop on the head of the case. The V-holder for the bullet allows one to hold the round down the same amount each time when set up properly. It is much easier to use than the Sinclair.
I'm getting very different runout readings from the two tools. On the Bonanza, it is showing about .0015" runout, whereas on the Sinclair, I'm getting more like .006". However, this latter may be more due to my problems discussed above than any actual runout in the round. Just FWIW, the case is an unfired, neck-turned Norma case, with a Bart's 68-gr. 6mm. bullet.
Any thoughts on this?
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