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Sort by bearing length and by weight?

 
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  #22  
Old 02-03-2012, 04:05 PM
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Re: Sort by bearing length and by weight?

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Originally Posted by Mikecr View Post
To measure bearing length you would first qualify datums that are base angle, and ogive radius, so that bearing alone is isolated.
Then, MAYBE, very difficult testing might show an affect of bearing variance to MV.
Until then, it is merely mob murmuring..
Isn't that what the tool does? It's not measuring from the base of the bullet, nor the nose.......
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  #23  
Old 02-03-2012, 04:51 PM
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Re: Sort by bearing length and by weight?

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Originally Posted by Bart B View Post
There are at least two others inside; jacket wall thickness is one.
True Bart. There are a lot of things to consider before tossing bullets, -or keeping bullets, based on measure.
Jacket thickness and variance affects stability and would be compared with a Juenke ICC. Same with core depth, which can be checked with a special indicator anvil.
We could benefit from a tool for meplat measurement, which is tricky, and really a bunch of other things..

But I suspect that until we have this, most shooters will continue to generalize value beyond rational in what they have today..

esshup, the tool is often used both with and/or without it's base.
And yes it does measure from the nose. The indicator anvil rests on the nose.
With qualified base angle, ogive radius, and appropriate tool leade angles, the base would be used to compare bearing only(isolated).
Even this is not a 'measurement', without a standard for indicator zero.
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  #24  
Old 02-03-2012, 05:41 PM
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Re: Sort by bearing length and by weight?

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Originally Posted by Mikecr View Post
day..

esshup, the tool is often used both with and/or without it's base.
And yes it does measure from the nose. The indicator anvil rests on the nose.


Your tool is dfferent than mine.

Bearing Surface Comparators
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The Truth Is Not Always Good For Business!!
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  #25  
Old 02-03-2012, 07:16 PM
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Re: Sort by bearing length and by weight?

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Originally Posted by Boss Hoss View Post
I have the same tool with the exception of using the stepped bottom piece on the dial indicator as well. There's a machined teflon sleeve that fits into the one that I use on the indicator, that is a snug fit to the indicator stem. There is a hole drilled thru it, and the stepped part is threaded.

I rotate mine a bit too to get it "seated", and use a round plastic headed thumbscrew instead of an allen head. But, basically that unit and mine is exactly the same in how it works, and how it measures.
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  #26  
Old 02-03-2012, 08:28 PM
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Re: Sort by bearing length and by weight?

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Originally Posted by Boss Hoss View Post
Your tool is dfferent than mine
Same tool, nothin rare about em.
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  #27  
Old 02-03-2012, 09:45 PM
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Re: Sort by bearing length and by weight?

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Originally Posted by Gene View Post
Trim length consistency. Or maybe that is external.
I'd say it's external. Whatever it is, it will determine to some extent the meplat shape of a hollow point.

The other internal thing is balance. With perfect dimensions in jackets and cores before they're seated and the ogive formed, the core may not be perfectly uniform around the inside of the jacket. Maybe the lead's not perfectly homogenous; one side's heavier than the other.

A friend spun some 30 caliber match bullets that had been run through an optical comparator to ensure uniform outside dimensions. Spun at 30,000 rpm, the worst unbalanced ones flew out of the collet holding them. Best ones drew the least amount of current to the motor spinning the collet; evidence there was no unbalance to load the motor bearings up and require more current to spin it up to speed.

Those perfect bullets shot an inch or less at 600 yards; the others worse depending on how much unbalanced they were.

Bullet companies shooting bullets through chronographs and timers have observed that bullets leaving at the same speed have different BC's. That's caused by the slight unbalance bullets have; the more there is the more drag the bullet has so it's BC will be lower.

All of which, to me, means that measuring all the static properties of bullets then sorting them into "perfect" and lesser lots, those "perfect" ones will still have some degree of unbalance that'll cause small accuracy issues. So it's gonna be hard to differentiate between what causes inaccuracy, slight unbalance or mechanically measured differences.
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  #28  
Old 02-04-2012, 07:03 PM
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Re: Sort by bearing length and by weight?

I was coaxed into sale of my Juenke..
Maybe some day I'll take on the challenge of building a bullet spinner of sorts.
Something similar to Vaughn's pneumatic, or maybe like your purely electrical.

I agree that imbalance, and poor release from the muzzle, are very real factors.
We can manage crown quality and reduce muzzle pressures with cartridge design and load/barrel length/twist choices. But a wacky bullet is still bad news.
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