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Old December 27, 2013, 04:54 PM   #1
Pond, James Pond
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Is it me, or is it Lee?

OAL. I know this has been covered before and I myself touched on it some months ago, but I really need to beat this drum tonight...

At the end of it, I'd like to know if I'm doin' it wrong, my kit is not up to task or it is actually not such a big deal.

Tomorrow I am off to the 100m range to try out my OCW loads and so tonight I made the finishing touches. When I first painstakingly measured up my OCW selection of loads and seated the bullets, I was still not sure what my distance to lands was in my chamber and so I seated the bullets way out in order to seat them to the desired OAL later. That being this evening. My chamber comes to 73mm or there abouts. That means that my OAL limiting factor is mag size, not chamber and my max OAL is 2.8" or 71.12mm. I opted for 71mm dead to avoid and feeding issues in the mag.

All the cases are neck-resized, trimmed Norma brass, and all have Hornady A-max .30 Cal 155gr bullets in them. So, I foolishly expected the OAL to be bang on the same for each case I put in the press, but after seating them all with my die set to 71.000000000mm, I found a max length of 71.12mm and a min of 70.85.

That is under a third of a millimeter, so part of me is thinking that this is no big deal. But then if I am trying to develop precise shooting loads, all parameters should be the same, so why the difference in OAL when all components are the same.

So is it me, the Lee, or no biggie?
Even if benign, why the difference?
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Old December 27, 2013, 04:57 PM   #2
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I don't load rifle, but I know it's possible that slight tip deformation during the seating process can alter OAL ever-so-slightly.

So, how do they shoot?
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Old December 27, 2013, 05:02 PM   #3
Pond, James Pond
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Give me a chance!!

I only posted 10 minutes ago and you're already expecting me to have shot them!

It's just gone midnight here, so you'll have to be patient and wait till tomorrow!!
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Old December 27, 2013, 05:02 PM   #4
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Ah, time warp.
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Old December 27, 2013, 05:19 PM   #5
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Not every bullet is exactly the same length, there is some slight variation. Where the die meets the bullet is mostly not length specific, so where the die makes contact with the bullet and is seating to the same spot everytime. Unless the die is moving...whats the variable? Grab a few bullets out of the box and measure them, you will see slight variations in length.

Honestly I wouldn't worry about it too much.
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Old December 27, 2013, 05:47 PM   #6
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Your seating die doesn't seat to the tip of the bullet, it seats to a part of the ogive. Hence the variability when you measure from the tip.

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Old December 27, 2013, 06:01 PM   #7
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If your dies aren't satisfactory, try these:
http://www.forsterproducts.com/store...23&catid=19938
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Old December 27, 2013, 06:08 PM   #8
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I agree with those above, it is the bullet that is causing your issue. If you have a bullet comparator you can measure from the ogive and see that each cartridge is the same measurement, it is the length of the bullets tip that is causing your problem.
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Old December 27, 2013, 10:02 PM   #9
Peter M. Eick
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As others have said, it is the fact that the bullets are not all the same length. This is especially true of HPBT's. Measure a 100 of them for fun and see the difference. Also as Jimbo points out the seater pushes at a particular radius point on the bullet, not the point so it contributes to the problem slightly.

For general shooting "don't worry about it". For precision shooting, sorting each bullet to the same weight and length "may" make a difference but it sure helps the mental aspect of knowing you have everything the same.
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Old December 27, 2013, 10:26 PM   #10
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Its a bullet problem. A-max is a piece of junk. It is typical Hornaday no quality control. They might call it a match grade bullet, but it is far from being a match bullet. I tried to get them to shoot when they first came out and quickly gave up on them. All the long range shooters I know have had the same experience with them. That experience is decent groups with quite regular extreme flyers.
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Old December 27, 2013, 10:33 PM   #11
Tex S
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That is about .011" of variation.

I usually write off about .005" of variation, but I must say I would be concerned about anything over that.

It is highly unlikely to be a die/press issue. I'd look at the bullets you are using.
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Old December 27, 2013, 11:14 PM   #12
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Quote:
Its a bullet problem. A-max is a piece of junk. It is typical Hornaday no quality control. They might call it a match grade bullet, but it is far from being a match bullet. I tried to get them to shoot when they first came out and quickly gave up on them. All the long range shooters I know have had the same experience with them. That experience is decent groups with quite regular extreme flyers.
My experience has been different.

While I haven't shot any of the 30 cal 155's, I've shot plenty of the 22 cal 80gr Amax bullets. They are pretty popular on the 500 and 600 yard High Power lines. I also know several tactical shooters that swear by the 30 cal 178gr Amax.

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Old December 30, 2013, 09:58 AM   #13
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It's you, get a bullet comparator and measure the same lot of ammo. You will likely get more repeatable results than measuring from the bullet tip. There are better seat dies like the Forster or Redding that can help too. Did you look at runout? That will be a more serious issue than minor differences in OAL.
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Old December 30, 2013, 10:31 AM   #14
Pond, James Pond
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Next question would have to be "What is runout?".
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Old December 30, 2013, 11:04 AM   #15
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In the world of ammo making, runout is the measure of co-axial misalignment of the cenerline of the bullet/cartridge to the cenerline of the bore in the barrel. It is measureable in the finished cartridge using a runout gauge. In layman's terms, it's wobble.

If you roll your ammo across a mirror and look closely at the tip of the bullet and its reflection you should not be able to detect any variance as it rolls across. Runout of .002" is acceptable for accurate loads. More than this and accuracy will suffer. Several manufacturers make runout gauges, I like the Forster system. The gauge is useful to identify steps in your ammo making process where runout is introduced.

Primary sources of runout include case sizing operations (pulling the expander ball up through the neck) and bullet seating (tilt) where each step will cause or add to a non-concentric combination. Variances in neck thickness in the same cartridge will cause runout too. That's why people who are interested in extreme accuracy turn necks to ensure uniformity.

Specialty dies are well worth the investment for reducing runout. The Forster and Redding seat dies with the tight tolerance sliding sleeve are excellent. Neck bushing dies have benefit as well.

Eliminating runout is what reloaders chase their tails over. Low runout takes a significant variable out of the shooting equation when striving for accuracy.
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Old December 30, 2013, 11:20 AM   #16
Pond, James Pond
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Now that was an excellent description.

The first proof is I understood it and the next is that I understood it easily!!

Thanks!!
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