Boolit concentricity?

[Mk42gunner]

Anybody ever check a cast boolit for concentricity by using one of the Juenke (sp) testers? Or anything similar?

I never tried, they were way too expensive for me back when they were readily available.

I have read a lot about voids in cast boolits, and the weight variation does tend to support that theory.

My rifle boolits have been good enough for what I want them to do, but I am not shooting any sort of matches with them either.

Just a question that keeps popping into my head, today I was at the keyboard and thought I would ask.

Robert

[Winger Ed.]

Look under and over them as they roll on a piece of glass.

It's not as good as a special tool, but it'll show you anything obvious.

[charlie b]

Yes. Both the bullet alone and the loaded round. The long nose bullets I use are not out of round with respect to the drive bands, ie, they do not move the dial (.001" dial). I checked the bullets alone since I nose size and wanted to see if that process upset the bullet in any way. It does not for the bullets I use.

I also visually check by rolling the finished cartridge across a flat surface. FWIW, my cartridge cases show no measurable runout at all (.308 Win) after sizing (Lee collet neck sizing die or Lee full length die).

After marking the cartridges that were slightly out of round I did see fliers from some of those rounds.

The surface of the bullets had an effect on the measurements. If there are any surface flaws then it affected the reading a lot (not surprising). Some of my powder coated bullets have a little 'orange peel' that also screws with the reading. An 'averaged' reading still shows decent concentricity.

After measuring a lot and looking at performance I found that a simple visual inspection was enough to get me close to 1MOA consistently. 97-99% of my loaded cartridges fit this criteria. Unless I am shooting for score I don't bother with this anymore.

Sent from my SM-P580 using Tapatalk

[ascast]

I assume your talking about a loaded round. Yes, do it all the time. Even on factory ammo when I shoot that. Readout should be under 0.002" or less for general shooting, minute of deer to 100 yds. For match shooting 0.001" or less. Anything in the 6-7 or above should be pulled, or shot where you don't care about hitting. I think it one of the best tools to have in your kit. I have rolled a lot of factory or military '06 and the correlation from low to high readout and tght to loose sloppy groups is so predictable and repeatable that it can not be disregarded. I mostly use one a friend/mentor made for me from a "V" block and fingergage. I also have an RCBS case gage station and find that parts well enough. Winger ed s correct about the glass -but the tool s better.

[ascast]

I looked for your Juenke tester: bullets only. have never used this type. I think if you do the math, it needs to spin at about 40,000 rpm or so to work as intended.

[M-Tecs]

The only people I know using the Juenke machine are using it to inspect jacket thickness consistency. I don't have a clue how it will do at detecting voids.

https://benchrest.com/showthread.php...ern-Juenke-ICC

The ICC will indicate three things:
1. Roundness of the test piece.
2. Jacket thickness variations.
3. Material density differences.

Therefore, you will see variations in a solid pin and a solid copper bullet as it rotates over the sensor simply because they are out of round.

Further, if you warm the test piece in your hands you will also notice the meter indication will change downscale but still show the same unit spread on the meter.
Conversely, a cooled test piece will shift meter movements upscale.
We recommend you use insulated tweezers when handling bullets and allow the entire set of bullets to be tested to come to the same temperature before testing.

Ken Juenke

http://www.bulletdoctor.com/BulletDoctor%20Home.htm

http://bulletinspector.com/vern_juenke_history.htm

[Four-Sixty]

Sounds like someone is reading Col. Harris.

After you sort out those bullets that are lightest, cut them apart to look for the voids. I doubt you could ever see one unless you get really, really lucky and cut the void just right as lead is so soft it probably closes up the exposed void in the cutting process. I think the only option is to toss out bullets at the extreme of your sort.

[popper]

Went round and round with a guy about this long time ago. 0.0005" diff in bullet dia gives more weight variation than any void! Loaded concentricity - roll around on a flat surface and watch for nose wobble. Stand on the head in a row and look for out-of-alignment. Eye is actually pretty good at seeing errors.

[ascast]

I looked for your Juenke tester: bullets only. have never used this type. I'm with popper on this one. Frankly, I don't believe in "air pockets" or "voids". Inclusions of light weight crap-yes, that I believe in. Squeezing he mold hard or loose will cause a slight weight variance.

[Mk42gunner]

Like I said, I was just wondering. Not something I am going to spend money on, maybe if I was into long range jacketed competition.

Robert