Case Runout Measuring. Comments on RCBS?


January 7, 2004, 10:40 PM
Looking to buy something to measure case neck concentricity, and bullet run-out.

I've looked at the top manufactures of case gauging tools, and I like the looks of the RCBS CaseMaster gauging tool.

You can view it at:

Price seems reasonable at Natchez.
Any user comments?


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Dave P
January 8, 2004, 08:40 AM
I use one of these all the time, but many people say that runout does not affect accuracy (unless it is extreme runout). Use good dies, brass and bullets and don't worry about it.

If you are new to reloading, I would keep this on the wish list, but spend your money on more importasnt tools first.


January 8, 2004, 09:42 PM
I've been using one for several years. Once I learned how to use it, I was well pleased with it. There IS a bit of a learning curve:cuss: , but patience and constant referral to the instructions will see you thru...

Hint: RCBS also markets a mounting plate that the "Casemaster" fits (as well as a lot of other things...)on. I mounted mine to this, and C-clamp it to my bench wherever I need it.:D


January 8, 2004, 09:52 PM
Well Dave;

I've been reloading for some years now, so my current two threads are based on my adopting new techniques.

There's something wrong with my .30-30 loads. It's back to the drawing board for a complete reexamination of the entire reloading process for this caliber.

Rather than just throw out & replace dies based on speculation, I'm thinking it's better to buy a ~$50.00 tool to measure the results of the case forming and bullet seating, etc.

The tool will be useful for all calibers, and I can probably even use the dial guage in other projects as well.

January 26, 2004, 09:19 PM
Dial indicator's a good thing to have, no need to pay $50 though.

Get one off e-bay for $25 or so w/ a better magnetic base (2 point adjustment arm, useful for things besides reloads) than the RCBS base.

January 28, 2004, 03:36 AM
Measuring runout is one thing - easily enough to do, & it may pay some divendends, but, concentricity is something altogether different & total runout is something altogether different & important regards total alignment (which is what they/you are attempting to describe) - trust me, I'm a metrologist.

"Concentricity," in normal terms is what would be described as a total alignment of the entire length of a bullet - not true.

Seriously, & it's a "measurement-thing" that some, try to impress the unknowing.

Ya know what?

The best way to acheive a decnt load is o use decent dies, proper load development, blow off the "eccentric" BS & load to the best you can.

I'll explain further after all the rest explain why I'm wrong. ;)

January 28, 2004, 02:27 PM
("What's runout," he whispered?)


January 28, 2004, 06:27 PM
Runout is a measurement of deviation in round objects. I.e. how "round' or well centered is it? (with today's excellent manufacturing processes, excessive runout is more likely to be cause by centering problems rather than less than round parts, resulting in a wobble from centrifugal force, not good in high RPM apps.) I dial indicate the fans and clutches in my model helicopter engines, and they may be out of round by a couple thousanths of an inch, any more would cause unacceptable vibrations. The "runout" is how much the dial indicator moves when the object is turned........

I've never actually dial indicated any bullets, but would imagine any runout in excess of a couple thousanths or so would indicate a manufacturing problem. As Labgrade noted, its not that big a deal in this application.......

January 28, 2004, 07:14 PM
Thanks. I didn't mean to hijack the thread - I thought "concentricity" and "runout" were the same thing.


January 28, 2004, 07:46 PM
This may help you visualize it better.....

If you have a "mystery problem" you can't seem to get ironed out, runout may be something to check. Otherwise I wouldn't worry about it too much.

January 29, 2004, 12:33 PM
It could get complicated, but doesn't have to be.

The "measurement of concentricity" is actually that of eccentricity - the state of being "out of alignment" with your base axis. Concentricity itself can't be measured 'cause if you're in total alignment= there's no deviations.
Kinda a same-same thing for balance - different things, but what you're measuring is an "out-of" thing.

Unless dealing with absolutely known-to-be perfectly true chambers, you'll have some mis-match with your round sitting pretty, & too, if it was perfect, it'd be tough to stuff the round in anyways. There'll always be some slop.

A nicely straight bullet (seated into the case) & properly aligned is always a good thing, but I'd betcha beck tension & a very consistant load makes more difference.

I'm no bench rest guy at all, but have a rifle or two that turns in groups that all but approach 1-hole accuracy (.19" for 3 shots) & seems way plenty for anything other than the most absolute in accuracy.

Those BR-guys are crazy! ;)

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