bullet runout

[Tom Thomson]

Does anyone check bullet to case concentricity and/or skew? How do you measure and what are your results? Can you correlate with group size?
tommyt (308)

[jonbearman]

Yes it does correlate with accuracy. There are a number of tools for measuring the bullet run out. From Hornady,, and a host of expensive others that are custom made.

[gotcha]

I measure with a Forster concentricity gauge although there are several such gauges available. See Sinclair Intl. site for several nice gauges. I've never seen any definitive studies on concentricity versus accuracy but it stands to reason that bullets that start straight into the lands would produce better accuracy. I try to keep run-out under .002". Anything with .004" run-out or more automatically become foulers. I've found that bullets jammed .010" or so into the lands will tend to reduce run-out when extracted and re-measured. (match barrels and chambers) Turning necks will also reduce run-out. Correlation? I can't honestly say yes. I do know that when I pay attention to the little details my groups get smaller and my confidence rises.

[Robinhood]

My buddy made this for me.
http://i1379.photobucket.com/albums/ah131/ProneoneProneone/View%20RO%20gauge_zpshd1rmlzr.jpg
http://i1379.photobucket.com/albums/ah131/ProneoneProneone/comp%20ro%20gauge_zpsmglfmxzl.jpg
He made 4 of them and our group uses them regularly. There is one where the bearings are a little farther apart. They where made out of scrap bin material which made it cool. What we have found is with correct neck tension, annealed when needed, and good dies you rarely will see one with more than .002 or .003 R.O.. Rather than straighten the ones above .005 we use them as sighters.

[Hotolds442]

Robinhood, you have a nice tool!

[yobuck]

Has anybody just marked the case head with a marking pen then insert them all into the gun the same way?

[Tom Thomson]

yo
not yet altho it's going to be difficult to tell what diff that makes
tommyt

[DennisPA]

David Tubbs clocked his rounds by the runout. If you look on YouTube there is a couple hour long vids talking about reloading. I think they are from the early 90's but most of his process hold true today.

[Robinhood]

Has anybody just marked the case head with a marking pen then insert them all into the gun the same way?

Some of the best shooters I've competed against do. Most of them were Benchrest guys.


Robinhood, you have a nice tool!
Thank you sir. What you dont see is where I spot faced them the diameter and depth of a round magnet in two places on the bottom. I epoxied them in flush. To adjust for different cases you just slide it over and put enough camber in it to drive the case rearward as it is turned.