Concentricity guage

Made One

Had a steel plate cut, about 4" by 8" by 3/4". Took an aluminum strip the same length and about 1 1/4" wide and 1/4" thick. Got some ball bearings (slingshot ammo). Drilled depressions for them in the aluminum and glued them in. Glued the aluminum to the steel along one side. Then got a dial indicator with a magnetic base. I can position it anywhere along the steel plate. The pairs of ball bearings are at various distances apart to accomodate different cartridge lengths. I can measure anything from a 6 PPC to a 7mm Magnum.

I know a picture would be better, but I'm lazy. This thing works great and is fully adjustable.
 
I like the Accuracy One concentricity gauge best. The concentricity gauge made by 21st Century Reloading is also nice, but I think the Accuracy One is easier to set and adjust the indicator. I would definitely recommend one that spins the cases with a drive wheel rather than by hand.

Here is the link to the Accuracy One gauge.
https://bullettipping.com/products/concentricity-gauge/
 
Has anybody done real test with a tightneck BR rifle to see the actual effect of rounds that the bullets run out. I don't want mine to runout, but has anybody done a blind test and where can I find it.
 
Butch Lambert said:
Has anybody done real test with a tightneck BR rifle to see the actual effect of rounds that the bullets run out. I don't want mine to runout, but has anybody done a blind test and where can I find it.
Click to expand...


Butch, I think they did a good while back and it didn't mean a rats rear end. but I still use one to check things out if have a problem..... let me see where I put that thing... LOL...jim
 
Butch Lambert said:
Has anybody done real test with a tightneck BR rifle to see the actual effect of rounds that the bullets run out. I don't want mine to runout, but has anybody done a blind test and where can I find it.
Click to expand...

Don’t think so, and you got somebody like Boyer stating they’re not needed but With all the $ we spend on BR stuff I kind of want one simply to check my process I guess.

Thanks for the thoughts guys.
 
I'm sure not one to shoot rounds with run out, so I make my own seaters to pretty much eliminate it. I'm thinking in a custom chamber that you may not lose much.
 
The concentricity gauge is nice to see if you have any issues with your reloading steps. I’m pretty new to loading 30 BR and found little to no runout in sized case necks, but the seated bullets had .004 - .005 runout. Turned out that there was too much neck clearance with my in-line seating die to get the bullets seated straight. New seater fixed the problem. I think if your sizing is not concentric it could be an issue if you use minimum neck clearance. Not sure that it matters, but it can’t hurt to shoot ammo as good as you can make it.
 
butch lambert said:
has anybody done real test with a tightneck br rifle to see the actual effect of rounds that the bullets run out. I don't want mine to runout, but has anybody done a blind test and where can i find it.
Click to expand...
yrs ago i made my own seater bullets seated were bad gun shot like house afire .
 
I'm learning there is a big difference in seaters. I recently bought several sets of Hornady New Dimension Match Bushing Dies because they came with a micrometer seater. I quickly found that they don't hold the case aligned well. You have to make sure you push the rim all the way beck into the shell-holder, and then you are dependent on the precision and alignment of the shell-holder. Probably explains whey they were inexpensive. I just now read some reviews on the few sites that carry them and there were complaints about runout.

I have Redding and RCBS micrometer dies that support the case body and I have no issues. Truth is, the micrometer adjustment is not necessary. With my Wilson seaters, I quickly learn how much 1/4 turn of the adjustment screw affects seating depth. I think I remember it is about 12 thousandths.
 
I had some rounds that were out a few thousands verified on a gauge, I shot them side by side with rounds from a new FL die showing much less RO without any difference in POI so I asked a couple of fellas with world records how they deal with RO the consensus was that it was not a issue, there were bigger things to worry about so I sold my gauge.

I also wonder how a .243 bullet boat tails down a .237 bore for 28 inch’s on its way to the target.
That doesn’t seem possible to me but then I’ve never been the sharpest tool in the drawer either.

J
 
I don't think it would matter at short range

The theory is that runout will cause the bullet to precess more, with a corresponding increase in drag / drop in BC. It would be a small change and I don't think you'd notice except at extended range. (And it's questionable whether you'd notice there.)

GsT
 
SPJ said:
I had some rounds that were out a few thousands verified on a gauge, I shot them side by side with rounds from a new FL die showing much less RO without any difference in POI so I asked a couple of fellas with world records how they deal with RO the consensus was that it was not a issue, there were bigger things to worry about so I sold my gauge.

I also wonder how a .243 bullet boat tails down a .237 bore for 28 inch’s on its way to the target.
That doesn’t seem possible to me but then I’ve never been the sharpest tool in the drawer either.

J
Click to expand...

That's the diameter across the top of the lands, which simply engrave the [bullet] jacket - the groove is .243, or, "close to it". ;) RG
 
Kookie said:
I’m pretty new to loading 30 BR and found little to no runout in sized case necks, but the seated bullets had .004 - .005 runout. Turned out that there was too much neck clearance with my in-line seating die to get the bullets seated straight. New seater fixed the problem.
Click to expand...

This is more common than most realize. ;)

Good shootin'. -Al
 
SPJ said:
Yes of course, quite right.. So with this bullet being engraved how does a couple thousand of run out effect trajectory
Click to expand...

The gauge may be, showing misalignment (out of parallel/tilt), as opposed to concentricity (or, a combination thereof). A tilted bullet may result in what the gurus call, "in-bore-yaw", which means that the center-of-gravity will be off-set (eccentric), or, out of balance (the bullet WILL swage & conform the the hole). Thus, unless the misaligned bullets are indexed, one could expect greater dispersion, due to random inertial moment toward the off-set. :eek:

In my early dayz of searching for BR precision, I did experiment with indexing non-turned cases & loaded rounds: indexing the out-of-whack ammo - say, the off-set at 12:00 O'clock - did result smaller group averages than did blind/random and deliberately chambering & firing at all points of the clock. RG
 
Interesting observation, although I’m not as seasoned as others I’ve had the opposite experience testing at 550 and competing at 600 yards. The term “in bore yaw” is what I was touching on the other day which again not a Guru by any means find it a tough pill to swallow.
A possible topic for a good thread.....
Thx
J
 
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