Concentricity gauge

[mdi]

Ninety five+ percent of my handloading for the last 30 years has been handgun cartridges and I have never had a need for a concentricity gauge for my handloads. I was looking at various vendors and at this time I don't care to spend $150.00+ on a tool that I'll use for just one rifle (maybe two if I get bored and measure my Garand ammo). So has anyone made their own? I like quality DIY tools so I might give it a try. I do know I'll have to purchase a dial indicator though...

BTW; have been a machinist/mechanic all my working days and familiar with measuring tools. Just wondering if anyone had any ideas on a concentricity gauge for rifle cartridges.

[lefty o]

v blocks and a dial indicator will do just about anything any gauge you can buy will.

[1066]

If you like making your own stuff you might get some ideas here - I made these in my home shop.



And a video of it working here:
https://www.youtube.com/watch?v=bRFn9GQYvSc

[flashhole]

1066 - Nice piece of work. Thanks for sharing.

[Iowa Fox]

1066 you should be proud of yourself, those are better than almost anything you can buy. I have a Forster & a Neco its hard turning the case smoothly with your index finger.

[jmorris]

I have built a couple. The last photo is an attachment I built for the first one that makes it a snap to measure case wall thickness.

[EDG]

If you are a machinist you can see .003 runout at the tip of the bullet by rolling your ammo on a smooth flat work surface like a table or counter top.

[flashhole]

I'm not a machinist and I can see that. I can see even less runout when I roll a case over a mirror.

[jmorris]

One of the more enlightening things about having one of these is you can measure cases before and after sizing and note the effect.

It taught me that the dies make more of a difference than what kind of press you use. Also the case might have come out of the rifle perfect but a die can cause it to become messed up.

Even little things like an expander pulled back through the neck can cause runout in the case.

If the case is not right, there is little chance that things get better when you stick a bullet in it.

[HangFireW8]

I've had the RCBS Case Master for years. The price is reasonable for what you get, since it doesn't just measure runout. You can use it to measure case wall thickness, find incipient case head separations, measure COAL, and probably some other things I've forgotten about.

It's the Case Master that got me from 3/4" to below 1/2" groups @100 for my 222, and still saves me from fliers with everything else.

[country gent]

Along with the concentricity gage a ball mike or thickness gage for checking wall thickness is a big help. Knowing the brass is concentric thickness wise around the case can answer a lot of questions. I believe the rcbs version can check this at the neck and just above the case head. Uneven wall thickness causes a lot of run out and banana shaped cases.

[mdi]

Thanks fellers. I don't have access to the machine tools I once had since I retired, so I'll prolly just find an inexpensive set up or just purchase one (but it would be used for only two cartridges; 308 and 30-06). I guess I was thinking about a simple DIY checker. I did have some "tube mics" that could be used to check neck/wall thicknesses. Now if I could just remember where I stored them 9 years ago...