Concentricity Gauge

[Brno308]

I got myself the Forster case and cartridge inspector that checks case concentricity and bullet runout. Grabbed a handfull of loads I did a while back and tested bullet runout. First 3 perfect with hardly any movement on the dial. Next 7 varied from .005 to .007. Next lot gave me .001 to .003.

The question now is how do I rectify this runout. Read somewhere of someone having drilled a hole in a block of wood slightly larger than the particular caliber, then inserting the load into the hole and manipulating same until no further runout. I need a more "scientific approach"

Any suggestions, what do you gents do?

[azsugarbear]

Currently using thehole/block of wood as well. I am sometimes able to straighten out excess runout by running the loaded case back up into the seating die, then turning case in shellholder and repeating 2-3 times. Seems to work about every fourth case I try. The rest (if they are just a few), become fouling rounds. If more than a few, I pull the bullets and start over with some addl. case prep. On the problem cases, I check for runout on the neck before loading again. Using Redding competition dies with bushing. Maybe going with the next size smaller bushing would help?? Looking for answers as well.

[Mikecr]

Originally Posted by Brno308

I need a more "scientific approach"

This starts with understanding of sizing, and a better tool.

Forster claims the following functions for this tool: "Neck wall thickness, Case neck concentricity, and Bullet runout"
-Use a ball mic with a stop for thickness
-Their tool indicates only a small portion of eccentricity
-Their tool in no way indicates 'bullet' runout, nor cartridge runout

As far as bending loaded ammo to solve a problem? NOT scientific, or well advised...
Better to learn how to make & measure(to verify) straight ammo.

[boomtube]

what do you gents do?

I find the cause of excessive run-out and prevent it. Trying to bend a bent loaded round straighter to improve accuracy seems a near hopeless endevor to me.

[5 Shot]

For me, it didn't seem to matter what I did, I still had lots of runout...then I started turning my necks.

I think the the thicker side of the neck was forcing the bullet off center (towards the thinner and weaker side) during bullet seating. This caused excessive runout on cases that had very good runout after sizing.

I picked up a Wilson Chamber Type Seating Die, hoping that it would cure my problem, and it made no difference. Once the necks were turned, all loaded rounds exhibited less than 0.003" runout.

[Brno308]

Oh well, will use those extreme runouts as fowlers. Since building those rounds I have upgraded to Redding S bushing dies and a competition seating die. I will be testing the new rounds on the Forster tool before going to the range.

In case you are wondering... I am anal about case prep and do go the whole 9 yards. I have a RCBS case neck thickness cutter but have yet to master this tool. Having problems with cutting too deep into the shoulder area as a result of the 20 degree angle/bevel of the cutter. Might just try and grind that back to say a 40 degree angle. Any thoughts on this?

[5 Shot]

I bought a 21st Century Tool, and they make the cutters in different angles to match the case. This helps to keep that from happening. I would agree that the 20 deg angle is a bit shallow.