COAL Variance Questions


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spartan00054
August 5, 2010, 12:56 AM
So I've reloaded a thousand rounds or so of .223 at this point using a Lee Challenger single stage press, and I've noticed a variance in case overall length of the rounds that are coming out. For instance:

Using 62 gr. FMJBTs from Widener's in fully processed once fired brass charged with 24.0 gr. of H335, my load data calls for cartridge overall length of 2.2550 in. When I have the die set to where most rounds are coming out at 2.2550 +/- 0.0020, I've seen variances from 2.2450 to 2.2610. Of course, I set the ones that are over 2.260 aside and seat them to within spec later. My question is why am I seeing this kind of variance? I understand that the bullets themselves will vary somewhat in length, but that shouldn't matter in terms of how much space exists between the bottom of the shellholder and the bottom of the die when the ram is shut, right? Also, in the past, when rounds fall below a certain length, I pull them and reseat them later. Should I be worrying about the ones that come out a little short?

TL,DR: I'm getting some variance in case overall length, why is this and how far off do they need to be before I pull and reseat the short ones?

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blackops
August 5, 2010, 01:38 AM
I understand that the bullets themselves will vary somewhat in length, but that shouldn't matter in terms of how much space exists between the bottom of the shellholder and the bottom of the die when the ram is shut, right?

Correct.


Should I be worrying about the ones that come out a little short?

If it is effecting your accuracy, I would say yes.

I'm assuming you have checked the lock rings on your die and inside the die itself.

spartan00054
August 5, 2010, 01:55 AM
Yes, I have checked the lockring and the internals... everything looks okay. That having been said, I'm not sure what I should be looking for in the die.

It's hard to say if it is affecting my accuracy, as I've pulled and reseated everything below that 2.2500 mark up to this point. Overall, these loads have performed pretty well, even with the level of variance I have accepted as normal. These are plinking rounds to be fired out of an AR, so I'm not looking for MOA performance, it's more of a safety concern for me.

ranger335v
August 5, 2010, 11:06 AM
Two things.

First, such tiny variations in OAL generally mean nothing.

Second, book OAL numbers are only for a starting point, mostly useful for new loaders who haven't yet learned how to find and use the best OAL for their rifles and loads. Actually, if a cartridge feeds and chambers no firearm cares a bit where the point of a bullet hangs in space.

OAL will vary because the shape of the bullets themselves varies a bit and how we operate the press also causes some OAL variation. If we aren't consistant our ammo won't be either.

All that really matters for accuracy is how far the bullet travels before contacting the rifling. Pick an OAL that seems good to you and develop your charge for that length.

Not sure why you think the distance from the bottom of a raised shell holder and the bottom of a die matters for OAL. ??

spartan00054
August 5, 2010, 11:46 PM
Ranger, thanks for the advice. As far as the distance between the raised shellholder and the bottom of the die goes, I meant that to my mind, the distance between the point where the case ends and the seating assembly WITHIN the die ends should be a static number. Or, at least as static as you get given the human error and variance in ram stroke you point out.

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