Spin Balancing Bullets

[Webster]

I searched internet and found out that machines have already been made to check bullets for rotational balance (about $850 in 2005). This is an older post. Interesting reading. I have never heard talk about this. Does any one have recent experience with sorting bullets by checking rotational balance? Has it dropped out of favor?

http://forum.accurateshooter.com/index.php?topic=823258.0

 

[JamesnTN]

I use to use a jeunke machine and still have it, I've found measuring bearing surface and sorting the bullets that way has yielded much better results.

 

[mikecr]

It's not 'spin balancing'

 

[Steve Blair]

It's not 'spin balancing'

[br]
I don't know, Mike. Look very closely at the 230 Hybrid (upper) in the attached image. There is some obvious "spin balancing" there.

 

[Webster]

I assumed that the bullet was rotated somehow and you got some indication of out of balance. How does the instrument work? What is it actually determining?

 

[M14AMU]

As useless as teats on a boar hog!!

 

[mikecr]

In no way does it check balance of bullets.
Really, it's an overall eccentricity(TIR) gage, that reads at a point near center of bullet bearing.
As Eric Stecker found: http://forum.accurateshooter.com/index.php?topic=2032821.0

I had one for a while and sold it off, because in my view bullet roundness effectively changes on firing in one barrel over another anyway.
As far as static or dynamic bullet balance, it's not seen here.
Even with an actual spinner like Vaughn's, the measure is in 'undistorted by your barrel' form, which would seem invalid. But I'd love to build/have/&test a version of it.

 

[WayneShaw]

A Junke measures, rather senses, the variances in jacket material. I've seen sectioned bullets that were showing these readings and sure enough it was easy to see how the jacket material was thicker and thinner.

This is the whole concept with the modern bullet jackets, they are very consistent in thickness. Considering a bullet spins in the hundred thousand RPM's, a differing jacket thickness does make a bullet un-balanced.

 

[mikecr]

It does not 'measure'. It's a comparator.

 

[bheadboy]

i and many BR shooter make and made bullets using B&A Dietch and Culver dies. among others.

The Sierra jackets were about the best you could get, uniformity was outstanding as the jackets were punched out of 'flat" material. i used .0001 calipers and dial indicators to check wall thickness, etc. usually less than .0002 variation.

after core seating and point forming bullet spinners were used, the base and ojive were held in concave shafts with a .0001 dial indicator stationed to read the variation in radius on the bearing surface of the bullet as it was rotated slowly.

those with more than .0002 runout were used as sighters etc. those with .0002 or less for matches,
the topic here is confusing as there is not a "balance" but a rotational uniformity concern, the core seating step eliminates any possibility of "air pocket" inside the jacket, and the "balance is a function of the "round ness or out of round ness of the bullet.

many BR shooters will sort factory bullets the same way with a "spinner" as i indicate above.

Competition BR shooters have long known this.

Bob