Inconsistent OAL length


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CMV
December 22, 2011, 06:13 PM
I'm getting .005 overall variance in my finished rounds. All the cases were trimmed to the same length +.002/-.000, but I found after chamfer/deburr I introduced an additional -.002 variation on some (maybe shouldn't have done that with the drill?). Anyway, my cases seem to have .0035 overall variation - between 1.7485 - 1.752.

But that shouldn't matter right? That should make some bullets seat a little deeper than others, but the OAL should be consistent right?

First thing I checked for was primers not fully seated. They look good.

I'm using Lee dies in the Lee Classic Turret press but not auto indexing. The dies are about as finger tight as I can get them. I'm pretty sure I read that I'm not supposed to tighten the dies into the turret ring with a wrench - only finger tight. Even so, if the die was backing out I'd get progressively longer OAL lengths, not one at 2.225, then 2.229, then 2.227, etc.

I'm checking my caliper between measures & it's staying zeroed.

What am I missing? I'm staying above 2.20 min OAL, but I shouldn't be getting .005 variation should I? These are the rounds I'll be working up with, so I'm reseating until they're all 2.225". I'm thinking 5 thou is enough to cause inconsistency but maybe it's not enough to matter - I don't know.

.223, 55 gr Hornady FMJBT, H335 poweder, CCI #41 primer, Lake City brass.

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rcmodel
December 22, 2011, 06:21 PM
What am I missing?You are missing a bullet comparator to use with your caliper to measure OAL of the bullet ogive.

Measuring OAL off the tip of the bullet will often result in that much variation.
Because all the bullets in a box didn't come out of the exact same forming die.
So the length varies.

Measure a few bullets before you load them and see how much they vary.
If you are within that error range when you load them, Fuggedaboutit.

Bullet comparator:
http://www.sinclairintl.com/.aspx/pid=34262/Product/Sinclair-Hex-Style-Bullet-Comparators

rc

W.E.G.
December 22, 2011, 06:27 PM
...or this

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/DPMS/StoneyPoint-FederalGoldMedal-base-o.jpg

NeuseRvrRat
December 22, 2011, 06:29 PM
yep, you need to measure off the ogive if you're serious about tuning OAL. i like the "insert style" comparators that clamp on your caliper jaw. i use hornady's version. sinclair also makes an insert style.

W.E.G.
December 22, 2011, 06:30 PM
Within a few thousandths, "too long" only matters when the rounds are a few thousandths too long to fit in your magazine.

Imagine my chagrin when I was loading magazines (with my handloaded match ammo) on 9/11, only to discover that the ammo that "just fit" in my 20 round mags was 0.003" too long to fit in my 30 round mags.

243winxb
December 22, 2011, 06:44 PM
55 gr Hornady FMJBT getting .005" COL variation = it's not enough to matter:)

Damon555
December 22, 2011, 08:12 PM
Unless your loading for benchrest shooting or just short enough to fit in the magazine .005 is nothing to worry about.

Walkalong
December 22, 2011, 08:35 PM
Yep, nothing to worry about at all, even with much better bullets.

W.E.G.

I thought I was the only one who had some of those old yellow Lyman dial calipers.

.223, 55 gr Hornady FMJBT
55 gr Hornady FMJBT getting .005" COL variation = it's not enough to matterAbsolutely. Despite the Hornady 55 Gr FMJ being better than most 55 Gr FMJ's, it is still an open based bullet which limits the accuracy potential substantially.

W.E.G.
December 22, 2011, 08:44 PM
Hey!

I'm not "old."

I'm just "seasoned." Like muy picante.

CMV
December 22, 2011, 08:53 PM
So I'm actually making the case lengths worse by getting them to the OAL measuring at the tip?

Walkalong
December 22, 2011, 08:56 PM
It just isn't the important measurement.

Remember, the seater plug doesn't seat off the tip, it seats somewhere on the ogive.

The measurement from the shoulder to the ogive where it contacts the rifling is important, although the various tools measure from the base of the case. Assuming the shoulders are all uniform from the base, this works just fine.

Walkalong
December 22, 2011, 08:57 PM
I'm just "seasoned."Well seasoned? :D

armoredman
December 22, 2011, 09:48 PM
Well seasoned or well lubricated?

I wouldn't worry one bit about variances that small, but I don't reload match ammo, just plinking ammo.

243winxb
December 23, 2011, 10:58 AM
So I'm actually making the case lengths worse by getting them to the OAL measuring at the tip? From Lee > Seating depth variation

There are a number of possible causes for overall length variation. One is the way it is measured. If you measure overall length from the tip of the bullet to the base of the case, remember to subtract the variation due to bullet length tolerance. The bullets will vary in length due to manufacturing tolerances (bullets with exposed lead noses are the worst in this regard) and this will add to the overall cartridge length variation. Remember that the bullet seater plug does not (or shouldn't) contact the tip of the bullet when seating, but contacts farther down the ogive. For a more accurate seating depth measurement, take the seater plug out of the bullet seating die, place it on top of the cartridge and measure from the base of the case to the top of the seater plug.
A single stage press can have as much as .005" COL variation, progressive as much as .010"

Constrictor
December 23, 2011, 11:13 AM
Lee dies are likely your problem, they like to walk out on me.

JohnM
December 23, 2011, 11:17 AM
Lee dies are likely your problem, they like to walk out on me.

:uhoh: :rolleyes:

cfullgraf
December 23, 2011, 11:24 AM
Hey!

I'm not "old."

I'm just "seasoned." Like muy picante.

That is one to remember!

RandyP
December 23, 2011, 12:59 PM
As others have posted, your finshed round OAL tolerance should not be any issue at all. The times I have taken some samples of new factory ammo and measured those OALs took care of any worries I had about my reloads. lol

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