Concentricity Gauge

[DanConzo]

Right on Lapua40x. The only thing you have to be concerned with then is the head being true. Brown Precision had a concentricity gauge -cartridge straightener on the market back in the early 70s, I don't believe it was on the market very long. If cartridges always need straightened, seems like you'd have to look at why it's crooked to begin with, as others have said. Good gauges are easy to make if you have a few tools, ball bearings, dial indicators and the other stuff is readily available.

 

[BoydAllen]

I have both types. More than one model of Sinclair, and an H&H. The Hornady makes one serious mistake. by supporting the back of the case on its rim, it ignores the fact that cases do not expand to the chamber in a way that guarantees that the rim is concentric to the body of the case, and this is not corrected by sizing, so you are virtually guaranteed that the rim is slightly eccentric to the body of the case forward of the solid head. As far as the virtue of one support method over another, those that support off of the body, depend on the shoulder being perfectly round, which it may not be due to the effects of brass thickness asymmetry, both in expanding under pressure, and from sizing. On the other hand, the bullet stands a greater chance of being perfectly round. Also, although readings of the same round are likely to be different because of the differences in how it is supported, this does not invalidate either. They are different because the measurements have been taken with tools that work differently. Both tools can be useful. When I use my H&H, I position the V block so that it touches the case near its head, but not along the full length of the block. Overall, I prefer to use concentricity gauges to diagnose die issues, rather than to correct the deficiencies of each round, but I am pretty sure that the minor straightening that I have done did not have a negative effect. It would take a lot more testing to prove that it helped. One thing that it is definitely good for is creating self doubt among some of the competition at a match ;-) The time that I was straightening every round as I loaded, several fellows came over to check one of their loaded rounds. I have loaned my unit to friends who subsequently bought one.

 

[Lazydays]

Boyd,

Built like a brick is one thing my neco is not... but then again, they say I could break an anvil.

Tom

my Neco sets ontop a slab of granit that is about 8" square. Found it in the trash and it was part of an old gauge. Works well, and uses the correct dial indicator for precision measuring. I'd rather have seen Neco build their gauge out of steel (8620 to be exact), and use thinner teflon pads to support the case neck. My Neco sets on three points, and that makes it set in a plane. Most of the others don't. Aluminum moves all over the place, and will change size just from the heat of your hands. Let alone a 100 watt light bulb.

Best thing you can do with the Neco is to order in a piece of 3/4" gauge stock, and use that for a base to set it on. But for shear accuracey the tooling balls are the best setup I've ever found. Plus it's simple and cheap.
gary

 

[Desert Fox]

I used Holland. It's a pain to turn it with your finger while holding the cartridge at the same time. But it serve it's purpose.

http://www.youtube.com/watch?v=uJrw6o7bZNY

 

[p5200]

Well, sounds like I wasted another 90 bucks on my Hornady model just my luck. :-[

 

[8nthatk]

It depends on the loading/resizing method IMO. However, for the sake of brevity…
I want the bullet square, straight and concentric with the shoulder datum line, (where first brass contact is made upon ignition). I want the datum line square and parallel with the case head. I’ll have clearance (however small) between the brass body and chamber walls, so this is less important to me, and not the point where *I* would anchor the brass to measure concentricity or run-out.

If the bolt face is square to the bore, and the chamber shoulder square, straight and concentric to the bore, and a reasonably tight neck…I will have fired brass that is very easy to keep straight when sized with a quality die and a good seater (Wilson for me) used.

If I was to use (ahem, fabricate) a gage to read and/or adjust the runout and/or concentricity, I would want to preload the brass squarley off the case head (if I knew the bolt was 100% square, the webb if not) into a knife edge stop on the brass’ shoulder datum line, and use a gage on the ogive. If I was jamming a bullet into the lands, I wouldn’t bother. Ideally, a precsion smithed rifle makes it unneccasary, and the gage described above is used as a reality check of smithing quality as well as reloading tools and technique.

 

[rwk]

Any one make own.

 

[mac86951]

Ideally, a precsion smithed rifle makes it unneccasary, and the gage described above is used as a reality check of smithing quality as well as reloading tools and technique.

Exactly, which is why a good concentricity gauge will help when hunting for accuracy from a factory rifle or intermediate reloading process.

-Mac