Concentricity Gauge build

[jmorris]

There have been a few times I have wished I had a simple little concentricity gauge dedicated to the reloading room for measuring runout in cases and to see how well bullets are being seated, so I built this one today.

There is a slot machined into the base plate that the bearing holders ride in with an extra wide slot under that so the nut plate has clearance. This makes it so I just need one Allen wrench from the top to set it up.



The bearings are .375 and set into the aluminum carriers with Devon, I used a 1/4" stainless rod to mount one of my indicators to and a 1/4" dowel to locate the back of the case.



Tested it out on a precision ground dowel and it works but I think I am going to add a spring loaded wheel with and o-ring on the OD to act as a "tire" that holds the case down and back against the dowel and give my fingers something a little larger to turn.

[ph4570]

Nicely done.

[PaulG67]

I like it, well done.

[reed1911]

Looks great. The only thing different I did with mine was to use two "V" blocks so it would accept a wide array of cartridges. I like the ball idea though I may build one just like it for bullets.

[kbstenberg]

Are the 4 bearings floating loose in there holes with a spring under each one?

[jmorris]

Are the 4 bearings floating loose in there holes with a spring under each one?

No, that would give readings that would vary with different amounts of pressure applied to the case, like the back of your truck squatting when you connect a trailer.

They are just there to provide 4 repeatable contact points. I made it so it would work for .17 hornet to 50 BMG.

[Petrol & Powder]

Very well made. Nicely done!

[dverna]

Thanks for posting. I have been looking at building something as the commercial units seem over priced.

[OS OK]

Had to buy one, didn't have the tools to make one...very nice work by the way.

One thing for sure...it was an eye opening experience to compare the .308W rounds made from 3 different die sets and to see the difference it makes in rotating the cartridge in the seater die a couple times when fully seated but, when you have a case neck that's thinner on one side than the other, it'll stick out like a sore thumb.
This gadget will either make you decide to not worry about concentricity anymore or it will make you a very persnickety loader...it doesn't lie and once you know the difference you have to change things in the loading process to live with yourself.
Mine almost pushed me to the limits like a bench rest shooter...I didn't want that so I set a max limit of out of concentricity to .005" which I believe to be pretty dang good.

Best-o-luck with your loading metamorphosis you have coming...it'll be interesting to hear the results of the effects it had on your handloading practices's.

charlie

[country gent]

On the one I made I cut the balls pockets with a ball nosed end mill. Drilled a small relief hole in the center so the radiuses located the balls and left them free so they can rotate with the case on thier centers. I used 1/2" bearing balls in brass mounts on 3/8" rods . The back rod is also used to mount the indicator.

[W.R.Buchanan]

I have had one of these on the brain for some time now, however mine has a wheel with an O-ring on it that rotates the cartridge so you can get more consistent readings.

I do like your Bearing Blocks.

Now you have to radius the edges and a anodize the thing so it looks all finished and professional.

Randy

[jmorris]

The wheel was what I was talking about at the end of the OP.

This is it with the wheel.



I have never been one that spent a lot of time making tools pretty. Would rather spend the time making them more accurate than pretty, not like I have to sleep with them.

[OS OK]

Morris...have you had the time now to look at some of your in stock previously loaded handloads...how do they bear out? Are you surprised?
On my gauge I have to hold the round firmly to keep that needle from bouncing like crazy just from inconsistent pressure.

[jmorris]

The wheel does help a lot to keep the case in place, a useful addition for sure.

Yes, I don't keep tons of ammo loaded, just in case I change my mind or want something else but it did confirm a few things I had previously learned down range but also suprised me on others. Like some loads I was never really happy with were out quite a bit and some belt fed "SAW" ammunition I have has less runout than some Federal "premium" factory ammunition.

Now that I have one I can see how I went without one for over 30 years though. Really just built it to see the difference between different size dies.

After its all said and done, it's not the end all tool, just another in the box.

[OS OK]

I agree, it's not the end all tool but...it opens the eye to what we have been taking for granted, ie. esp. factory loads.

Re. the SAW...my wife has been after me to take her to Nevada so she can shoot one of the multi-barrel electrically driven MG's. Says she loves that sound. Can you see a 68 year old Gramdma running one of those?

[turtlezx]

How much difference have you noticed in accuracy between say .003" and .015" for example ??

[M-Tecs]

How much difference have you noticed in accuracy between say .003" and .015" for example ??

I have been using a case run out gage for 40 years. I can't answer that. The gage is used to fix loading technique issue. Whether its on a single station or my 650's or 1050's my goal is to keep run out under .0015".

For my long range competition loads this is not a problems since I mostly use Lapua brass. Run of the mill brass .003" to .005" is normal.

[jmorris]

How much difference have you noticed in accuracy between say .003" and .015" for example ??

Well, I can't really say that for sure. I had some "ok" loads that we used for setting off tannerite @100 yds that always does the trick and that's about .006" out (you can see that they are "turds" with the naked eye") and seated to factory OAL. Always shoots under 3 MOA from a "decent" rifle. Being "factory OAL" they are for everything in that caliber I own.

I think more time trying out different ammunition chambered, not fired, then measured might tell another story in itself.

For many years, I know some have liked "long" loaded rounds that "kiss" the rifling. I have a suspicion that in doing that I am making them straight after loading them or, in other words, that they straighten being seated in the chamber/into the lead of the rifling. Not sure if I have the time and energy to fix what is not broken at this point but it would be nice to know.

I have not kept good enough records for most calibers, I am afraid, just found what I have been happy with and that's it.

Sort of like a man with one clock always knows what time it is and a man with two is never sure.

[W.R.Buchanan]

The wheel is definitely a plus. I also like your indicator. I have several Tenth Indicators that never get used, and would work well for this application.

Randy

[jmorris]

I had a little time today and built an H&H style gauge too.