What is runout? Been reloading for several years but have never heard that term until you guys started talking about it.
Thanks, 8point

In the most general terms it is the amount of mis-alignment between the bullet and the bore. It can be the case which is not concentric or the neck portion, or many little nagging demons. But in the end it is the mis-alignment which contributes to inaccuracy. Shoot straighter!

Thanks sako,

How do you check for runout?

This is the RCBS Casemaster tool. They cost around sixty bucks, and are very enlightening little devices.

As has been asserted in other threads here, the rifle must reach a certain level of accuracy before you will see the advantages of reducing runout. Also take a look at the "Types of bullet runout" thread, as all runout is not necessarily "bad runout."

Dan

Green 788,
What does that horizontal bar on the runout gauge do?

It has a 90 degree appendage that aligns with the mic ball on the gauge. You then fit the case over that bar, and you can measure case neck thickness, as well as case wall thickness. It's important to check case wall thickness just ahead of the case head, as this is a point that can thin and seperate with several sizings and firings.

Dan

Max503,
That is a probe used in conjunction with the dial indicator to test for case Head Separation.
Rick

Get one of those. It is a very good learing tool.

Excuse me Dan when I correct you. The long bar is for checking wall thickness of the body.
There is a short bar a bit higher which is for measuring neck thickness.
The long bar and its measuring capabilities is limited, unfortunately, as it is too thin and tends to bend.
Generally the case master is not bad, but there are other tools which are better - they are not designed for all tasks but one only (concentricity OR neck wall thickness): you get less, but in a superior quality.

You may want to have a look in Sinclair's online catalog www.sinclairintl.com , and www.realguns.com has an article about this topic, if I remember correctly.

You're right, of course...

I answered in haste, and blew that one... I would say that the springing action of that case head seperation bar shouldn't degrade it's accuracy all that much, as the mic ball on the gauge will follow the feeler bar as it springs up and down.

I agree, though, that there are better tools for making these measurements.

For all concentricity functions, I'm quite pleased with the Casemaster.

Dan

"....seperation bar shouldn't degrade it's accuracy all that much, as the mic ball on the gauge will follow the feeler bar as it springs up and down."
Sorry,but this is not correct.
The system has two zeros, one being the feeler tip and the other the bar the probe is to rest on.

When this bar is not rigid, the relating zero is missing and the results are not relyable.
And exactly this is happening when you try to find out the wall thickness with this flimsy bar.

As I am interested in wall thickness generally, this feature is quite interesting to me.

My idea is to check wall thickness in the body area as a feature of accuracy, i.e. if there are changes in wall thickness, the cartridge will move out of alignment when fired thus bringing the center line of the bullet out of the center line of bore.

It is easy to measure the wall thickness of the neck, and it is easy to turn it.
But to my understanding, imperferctions in this area are a sign for a crooked case altogether.

Turning the neck cannot remedy this - the case should be discarded or used for foulers or plinking only.

[ 02-02-2003, 12:36: Message edited by: waitaminit ]

Maybe we're using our units differently... I just align the feeler tip with the mic ball on the gauge and then slide the case over the bar, until the area in question is in the junction of the feeler tip and the mic ball of the gauge.

Rotate the case, and let it go. Look at the reading, and rotate it again, and read. I just look for relative movement on the gauge, I don't try to ascertain the actual thickness here. So long as there isn't a thin area ahead of the case head, you're normally fine. You can actually feel this thin area (if it is there) with a small, stiff wire such as a bent paper clip.
I always take my hand off the case before reading the gauge, and I've found that the readings are realiable for the purposes of detecting case head seperation.

Since you are concerned with case wall thickness, I can see why this unit doesn't meet your needs. Especially with bottle-necked cases, the feeler tip and the mic ball junction will be leveraged apart as the measurements get closer to the case neck.

Dan