Cartridge length variation

[The Sodbuster]

I suppose most most of us that handload and go to extremes to wring a tiny bit more accuracy out of a given rifle obsess over details.  One area of precision I come up a bit short in is overall cartridge length.  I adjust the seating die until I get the cartridge length where I want it, and then find length varying in subsequent rounds, sometimes by .006" or even a little better (not every round, but enough to trouble me).  I've decided there are 4 potential sources of variation and would like your feedback on them:

1.  Caliper.  The idea being my digital caliper isn't that precise, and that maybe my cartridges are all identical length, but my caliper isn't sensitive enough to determine that (it's a Frankford Arsenal digital caliper)

2. Seating die.  Perhaps my dies aren't precise enough to give ultra-consistent overall cartridge lengths (I have Redding, RCBS, and Forster dies).

3. Bullets.  Maybe my seating die is fine, but length variation is due to variability in length of the bullets I'm using.

4. Any combination of the above 3.

Without a 25 pound, heavy, benchrest rifle, maybe the length variance I'm dealing with doesn't matter.  But as I stated earlier, I obsess over small details.  Any comments or ideas?

[quickdtoo]

Figuring out the optimum COL was the tough part for me, now it's a piece of cake to obtain a starting point......

http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=62608

[longwinters]

Good questions.  I have thought about the same things myself.  I have the frankfort caliper.  I think mine is accurate because if I measure one cartridge, then another one and finally go back to the 1st one it will give me the same measurement again.  

I use the standard RCBS dies.  Cannot say how accurate they are, but do not see how they could not be consistent from one bullet to another.  

I tend to think the variations are in the bullets themselves.  In the spitzer types etc... you can see with just a look that the tips are not all the same.  I would think that the polymer tipped ones are the same deal.

But I am hoping you get more replys because this is good stuff.

Long

[KN]

You are exactly right about the tips. Cartridge length should technically be measured on the oglive (spelling?). Not the tip of the bullet. Book OAL references are there to insure your rounds will fit in magazines. They are not a hard and fast measurement. If you want to see how much variation you might expect from your loads, measure the bullet lengths prior to loading. You'll see the variations your talking about in the tips. At least with most bullets. Some of the "match bullets may be a little better.  KN

[jcunclejoe]

Sodbuster, I posted a message about this just a while back. It has something in the title about The Myth of Over all cartridge length. It is toward the bottom of page 1 in this category of Handloading for rifles and pistols.

Please give it a read, it may clarify how some of this works. I hope it makes sense. Please feel free to ask any questions and I'll see if I can be of any help.

I ran into the same thing and it drove me nuts until I figured out how to make it right and consistent.
Joe