Concentricity Gauge?

I have built a couple different ones. I really use them more for process setup. Once I have components, tooling and processes happy with one another there isn’t much use in them as results are consistent at that point.

They are a great tool to see what effect changes you make have though.

I use one to sort bulk ammo. You can pick the fliers out.

The style above is pretty versatile. You can move the bearings so they are contacting the body of the case, a spot in the shoulder or the neck.




Might give you some information, others will not, if you have something you cannot explain going on. You can check fired cases and re check every step of the way to see if and where error is imparted to the case. Narrowing the problem to the particular step that caused it. This is the most helpful use of them for me.

I also made an attachment for mine where I can slide a case over the mandrel and measure wall thickness of cases without causing any harm. Another helpful tool but has nothing to do with runout.



As far as shear speed and ease of use, this style wins.



It cannot be used to check just a fired case, then again after sizing, again post expanding, etc; however, if you are wanting to check every loaded round and have a bunch of them, it doesn’t take long to realize it beats the others in this one use.

Good information on this thread, for whatever reasons I have not seen any difference on paper out to 600 yards. I have not tried a side by side at 1000 however I would yield to someone who has results at long range.
Good dies and set up are the key imo

South Prairie Jim said:

Good information on this thread, for whatever reasons I have not seen any difference on paper out to 600 yards. I have not tried a side by side at 1000 however I would yield to someone who has results at long range.
Good dies and set up are the key imo

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That's because like all other things; SDs, ES, concentricity, etc. actual accuracy trumps statistics (to a point).

I've also got the Sinclair unit and it works well. I use it for initially setting up dies etc. and then to cull "rejects" with excessive run out. "Rejects" aren't discarded, they get their primers marked with an alcohol pen and shot art shorter distances.

I honestly think an awful lot of the precision loading steps are incremental improvements, and some of it is psychological to remove excuses... I know what my ammo/rifle can do, so in the end it's got to be me...

Another Sinclair owner here. When I started using this tool I found out what was causing the flyers that I was manfully taking the blame for! If your bullet is seated crooked or your case necks are bent those things will open up your groups. This tool helps you to find the cause and lets you change your process.

Industry standard for bullet concentricity is .002. With my gauge I can get that down to less than .001.
It does help. I have a 1970 Rem 700 in 30.06. I consistently shoot .75 MOA at 100 yards.

South Prairie Jim said:

Good information on this thread, for whatever reasons I have not seen any difference…

Click to expand...

I can say one thing I found out after I built a few of the fixtures and went back over loads that had been worked up.

I had some 22 Hornet loads that shot pretty good (.3” for 5 @ 100) but I knew we’re not perfect as a machinist eyes could see the run out. After fooling around with them for awhile, I realized that once the ammunition was chambered, it was fixed. Made me wonder how many of the “load to the lands” people were converted because they couldn’t seat a bullet straight.

I’m with @South Prairie Jim. You had better be able to shoot pretty stinking, ridiculously, incredibly, disgustingly small groups before you spend time sorting ammo by concentricity, otherwise it’s not spending time, it’s wasting it. I can’t shoot the difference in ammo to make sorting by concentricity fruitful - money is better spent to buy better dies and skip the time wasted rolling cartridges.

I have the old Hornady tool, the Sinclair, and just got the new Hornady tool. For me, they are toys to tickle my curiosity and take up shelf space, not critical tools in my reloading process. I shoot plenty small for the tasks I pursue, and these have no stake in that claim.

jmorris said:

I can say one thing I found out after I built a few of the fixtures and went back over loads that had been worked up.

I had some 22 Hornet loads that shot pretty good (.3” for 5 @ 100) but I knew we’re not perfect as a machinist eyes could see the run out. After fooling around with them for awhile, I realized that once the ammunition was chambered, it was fixed. Made me wonder how many of the “load to the lands” people were converted because they couldn’t seat a bullet straight.

Click to expand...

Your probably right, and when you think about sizing and chambering as with the stripped bolt method we are .002 bump after the bolt drops freely the headspaced cartridge isn’t touching the chamber shoulder and bullet seems to self center into the throat so we can’t have too much influence brewing unless we subscribe to in bore yaw and that theory.

Varminterror said:

I’m with @South Prairie Jim. You had better be able to shoot pretty stinking, ridiculously, incredibly, disgustingly small groups before you spend time sorting ammo by concentricity, otherwise it’s not spending time, it’s wasting it. I can’t shoot the difference in ammo to make sorting by concentricity fruitful - money is better spent to buy better dies and skip the time wasted rolling cartridges.

Click to expand...

I agree with this up to the point of thinking money always solves problems or even knowing if you have one without the tool.

If you wanted one to gain a little knowledge, I have spent more money to learn less in the past….

On the scale of importance, I would put one ahead of neck turning or primer pocket uninformer. Aka, not very high on the list of importance and far from a necessary tool.