Looking for input from people who do use a concentricity gauge such as a NECO, RCBS Casemaster, or other home-brew devices to check case wall runout. I'm attempting to do same with my NECO gauge, but I'm finding the directions a little... off, mainly because the test indicator pictured in the destructions is a different model/configuration than what I have (mine is newer), and basically, I can't really make it work that way without breaking/bending something.
One person I've spoken with uses theirs to 'spin' the cases and get a running TIR number; despite having several conversations w/ them about it I can't seem to manage the same technique with any degree of accuracy (needle swinging all over the place). I've tried marking four cardinal points on the case body and taking static readings... results seem to vary wildly there as well: one batch (fireformed, but cleaned inside and out) showed very little variation, another batch (virgin, but same lot) shows 2-3x as much runout.
If your lgess run out on the fired cases than new brass, I would think that is a good thing. I would expect my brass that was fired and then resized would be "straighter" due to a chamber that is cut straight.
Factory brass, is mass produced and getting it straight is not much of a concern.
As for the proper use of the guage, I will let someone else give you feedback.
I believe what you're experiencing is the sensitivity of the gauge itself. The run-out gauge is far more sensitive than a dial indicator, and that should be its virtue. Another thing here is that you're measuring more than case straightness and wall thickness; you're also seeing every ding and imperfection in roundness of the brass. The thickness measurement is showing additional parameters to what a ball-end micrometer will. Your fired and cleaned cases have reduced these other parameters so that wall thickness and straightness dominate the measurement.
I have every confidence that if you play with this thing a little bit and think about what you're measuring, you'll discover how well your NECO tool can serve you. I don't know how the new gauge is different from the one I have seen, but I expect that the change will mostly affect set-up.
Last edited by Winchester 69; 01-20-2009 at 06:45 PM.
After some polishing (okay, a LOT) I finally got the edges smoothed and the points rounded on the chord so it wasn't digging in to the case so it could actually rotate/spin easily. I also ended up running the case mouth over an expander mandrel... before the case mouth didn't always sit on the same step of the cone, which if it didn't actually hurt, sure drove me to distraction. Between the two, the readings seem to have settled down a lot. For better or worse, I'm trying to sort/cull Winchester .308 brass (which normally shoots pretty well *anyways*) into 'best' (for LR match use) and 'good' (for load development, practice, sighters, etc.) Firing each piece just to fire-form it for sorting seems a bit... wasteful.
You're right about the sensitivity of this thing... I'd hate to see what a test indicator in 0.0001 increments was like!
I'm not a competitor, but this is what I do to get right to the best brass in a lot:
For one, I use Sinclair tools, and to begin I measure thickness variance at the necks on 1000 pieces in a lot. This is a micrometer with a ball anvil and stand.
There is no need to fireform beforehand(for this cull).
I usually end up with ~150 pieces showing almost no variance in thickness.
If there was, I assure you it runs full length of the case, and will produce bananas down the road.
Then I prep(incl turning), and fireform these 150 pieces. When I pull em out of the chamber and drop em on Sinclair's concentricity gauge(bearings and dial indicator) they will show ZERO TIR. That is <5-ten-thou, as you cannot measure less on unpolished brass.
At this point I measure H20 capacity on each, and end up with ~85 pieces that match.
That's 85 jewels right there.
With custom dies -made with your reamers, you can wear out many barrels with them.
With the right load and an Oehler/20ft screen spacing, you'll see under 10fps of ES from these.
Using a Wilson seater blank cut with your finish reamer, and running each round over a Sinclair expander mandrel prior to each seating, you can produce loaded ammo with <1thou TIR off mid ogives.
I rake the rest into the trash, simple as that.
Brass is cheap.
I'll say here that Sinclair's tools are not bettered out there. Yes, there are fancier and more expensive turning and measuring systems.. Lotta pretty colors and promises...
None better than offerred by Sinclair.
Thanks for the input... thats certainly thorough! Unfortunately I need a little higher yield than that from a given batch... brass may be 'cheap' in the final cost analysis, but 1000 -> ~85 *perfect* cases.... wow! My hat's off to you, though, for your perserverance. I do have a few questions, if you don't mind.
What kind of brass are you starting with? I'm dealing with Winchester .308 Win at the moment - which is relatively cheap, but I do expect a fair (20-40%) of culls. If I had that sort of rejection ratio with say, the Lapua 6.5-284 brass I just purchased for $102 per box... I'd be a little disappointed, to say the least (and broke!).
Could you go into a little detail on your procedure for sorting by water volume? A while back I did a test of case weight to water volume to muzzle velocity... and found out the hard way just how poorly virgin brass water volume tracked w/ MV, so I understand that part. I'm curious if you have any tips/tricks for making it less... tedious, and more repeatable (I had a very hard time getting the meniscus level, even with some dish soap in the water - it made a noticeable improvement, but the whole process was still very, very long and drawn out). Also, in a recent conversation w/ Ed Dillon of NECO about QuickLoad, he stipulated to take some thick grease and use that to fill/seal the primer pocket for water testing, as spent primers had too much variability both in their own weight and in the voids for water to get into and fill, thereby skewing the readings.
The brand of brass doesn't matter as perfect is just that, in any brand. But the number of jewels found will definitely vary lot to lot, and depending on cartridge. I use Lapua, Norma, and Winchester. Norma is always consistant-in lot, and Win brass for WSSM/WSM is great(just too thick). My standard for reference here is Lapua in 223 and 6br.
You can get a higher matched count by neck turning and capacity matching. Here, runout will grow with each sizing, but that might not affect you really. Depends on the cartridge(mostly length), thickness variance in your lots of brass, and system of stress relieving(anealing). And your brass might be whipped before runout ever becomes an issue anyway.
You must fully fireform brass before checking H20 capacity. Don't even try it with new, or sized brass. Don't bother weighing cases either(meaningless).
I stand each piece on a scale with a plastic golf tee into the flash hole. I zero the scale. Then I fill the case to the mouth using an eyedropper. I've been adding a small bit of alcohol to my water, and I touch any meniscus with a tissue corner to flatten things. I record each case and when complete, I discard those leaving the pack.
Now kept together, this brass is no longer any issue down the road. It's right.