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Old May 16, 2013, 06:22 PM   #1
rebs
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over all length problem ?

I am loading some 223 using Mid South Shooters Supply's 55 gr varmint nightmare x-treme premium bullets, I believe they are made by Hornady. I weighed a bunch of them and about 98% were 55.0 gr. The biggest variance was .03 gr. Then I measured them for length and the were right at .710 with a varience of .003. They are very consistant in weight and length.
When I seat them I get a variance of 4 to 8/1000". Some come out right at 2.210 and they vary as much as 2.204 to 2.215. The seating die is adjusted and locked down so it isn't moving.
Why is there so much difference in OAL ?
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Old May 16, 2013, 06:26 PM   #2
Kimber84
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over all length problem ?

Not familiar with them, but I'm assuming they're polymer tipped? If so I would make sure your die is pushing on the ogive and not the tip..

I'm not a bullet engineer, but a variance of 3 thou is probably within spec and I agree isn't much.... Dunno though.

It could be a slight variance in the ogive of the bullet, though as well.

I'm sure others will have far better advice but its just what comes to mind first
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Old May 16, 2013, 06:29 PM   #3
steve4102
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All bullets will have some amount of variation when measure from the tip of the bullet. If you want more accurate and consistent OAL measurements, get a Comparator and measure off the Ogive not the tip.
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Old May 16, 2013, 06:37 PM   #4
Nathan
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My experience is that measured to the ogive, I get like +/-0.004", I think. To the tip seems more like +/-0.01".

Not sure why.
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Old May 16, 2013, 07:20 PM   #5
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I doubt you wold see a difference in accuracy in them if you shoot them. As long as they are not too long to load in your magazine, and not so short they catch under the lip of the feed ramp they should work just fine.
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Old May 16, 2013, 07:47 PM   #6
rebs
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These bullets are HP's not tipped.
I know the seating die uses the ogive to seat the bullet, but I didn't think there was that much difference between bullets of the same brand type and grain. I had thought that with the die locked down they would be more uniforn in OAL.
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Old May 16, 2013, 08:41 PM   #7
higgite
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Are you crimping? With the seater die?
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Old May 16, 2013, 09:07 PM   #8
rebs
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no crimp
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Old May 17, 2013, 08:05 AM   #9
Kimber84
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over all length problem ?

There's just so many tolerances that take place throughout the manufacturing process that its a wonder we're able to build anything that works.

I'm sure a perfect bullet could be manufactured, but high runs of production on such a part would become difficult and expensive. I would just shootem up and see how it does.
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Old May 17, 2013, 09:06 AM   #10
Unclenick
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Rebs,

The most likely thing is the bullets are off of mixed sets of tooling. Use your bullet comparator to sort the bullets themselves into groups 0.001" different in length from bullet base to ogive. Line them up and you may find they cluster around several distinct values, rather than making a nice bell curve. Each cluster represents the output of a different tool set, and you may find accuracy differences doing it that way, as well as getting more consistent COL's.
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Old May 17, 2013, 09:23 PM   #11
Bart B.
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All of the finest match bullets made with the same set of forming dies will have slightly different shaped ogives. The jacket material's not all exactly the same. Niether is the lead core. There will be variables. Sierra Bullets admits their bullets' ogives are not all perfectly shaped for a given lot of bullets even though the final stage of forming them is the pointing die that shapes the ogive to a point.

Seating a batch of bullets that have the same exact length from case head to the reference diameter on the ogive will have different over all cartridge lengths from case head to bullet tip. All those bullet's tips do not swage down perfectly every time. Not a big deal as the best of them will shoot under 1/4 MOA at 100 yards.

Here's another variable that few folks even think about. Rimless bottleneck cases have their shoulders hard into the chamber shoulder when fired. The reference diameter on those case shoulders are not all the same distance from the case head; there's a few thousandths spread. So, that spread and point is what actualy controls how far the bullet jumps to the lands when fired and the bullet irregularaties also compound that distance variance. With all bullets having exactly the same shape and dimensions, bullet jump to the rifling will have a dimensional spread equal to the case headspace variable.

Just shoot the darned bullets. A few thousandths spread in jump to the lands may be shown in tests with rifles that shoot those bullets no worse than 1/10th MOA at 200 yards.

Unclenick, Lapua was known to use 3 or 4 sets of forming dies making a lot of 30 caliber match bullets some years ago. Comparing them in an optical comparitor showed 3 or 4 distinct ogive shapes in a given lot of their D46 match bullets. Sierra uses the same set coin, cup, draw, trim, head, rim, core and pointing dies for a given lot of bullets. I don't now about other company procedures; they may use 2 or more sets of dies
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Last edited by Bart B.; May 17, 2013 at 09:29 PM.
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