Concentricity Gauge

[joelkdouglas]

I have a new toy/tool/nemesis, a Sinclair Concentricity Gauge.

For those of you with a concentricity gauge, do you cull rounds that exceed a certain concentricity?

As in, if concentricity exceeds 0.003 you use that round for a sighter, or 0.005, or x?

Thanks gents.

 

[.300winmag]

I've got a concentricity gauge and I have fine tuned my reloading dies with o-rings and very small amounts of filing so that over the entire cartridge, I have about 0.002" of run out at any given point over the cartridge, from the base to the bullet. I don't know how much run out it would take for you to notice any difference honestly, but the less there is the better. What you might try is load rounds and measure the run out and sort them based on the run out. Then, take them to the range and shoot them at say 300 yards or the farthest you plan on shooting them at a game animal (I don't think you'll notice very much change at shorter differences and the differences should be amplified at longer distances). After shooting all the different run outs, if you find that say 0.005" of run out produces a 4.0" group at 300 yards but 0.003" run out produces a 3.0" group at 300 yards, then maybe 0.003" of run out or better is what you should shoot for if you feel it is necessary.

In terms of how to adjust your dies to make them more consistent, I would start by contacting the die manufacturer and asking them how they suggest you go about doing that.

 

[SJB358]

Good topic, this is something I need to learn more about for sure.

 

[rick smith]

First check the concentricity of a fired unsized case from your rifle. Then check it at each step in the loading process. The seating stem can be a big part of the problem especially with VLD and some match bullets. Take the seating stem out of the seater and fit it over the tip of your bullet. The tip should not bottom out in the stem before the ogive of the bullet is contacted.Rick.

 

[.300winmag]

First check the concentricity of a fired unsized case from your rifle. Then check it at each step in the loading process. The seating stem can be a big part of the problem especially with VLD and some match bullets. Take the seating stem out of the seater and fit it over the tip of your bullet. The tip should not bottom out in the stem before the ogive of the bullet is contacted.Rick.

Excellent piece of advice.

 

[Kodiak]

If a certain lot/batch of cases seems to always have an unacceptable run-out, annealing those cases may solve the problem.

I also had a rifle that was not custom chambered properly. Once I found this to be true, I marked the rim on all of the cases shot in that rifle, so they could be indexed into the chamber in the same manner at each firing.