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coloradokevin
May 8, 2008, 04:10 AM
Well, with the helpful advice from everyone here, I've finally loaded up a few test pieces!

Interesting results, which have taught me a couple of things:

1) Either I am dumber than I thought and just built bunch of little bombs for my gun, or my fears of "double charging" are moot in some powder/brass combinations. I'm using H4895 and at 25grains it filled each cartridge to the shoulder... Sure couldn't fit a double charge in that case!

2) I still don't seem to fully grasp why things come out the way they do... I used a piece of factory loaded ammo as a basis for comparision, and set my bullet seating die up. My finished product came out to 2.194 inches COAL, which my books show as being within SAAMI specs (between 2.165 and 2.26"). But, two of my first ten cartridges came out at 2.190 and 2.189 inches, for a variation of .004" and .005" from the standard measurement.

I'm just building plinking ammo for the moment, so I'm not really too concerned with this variation for that purpose. However, as I try to improve my ammo for other purposes, I'd like the COAL to be the same. Any idea why this might have occured? I took new Winchester .223 brass, resized it, trimmed to 1.751", chamfered and debured the case mouth, then threw in a primer, powder, and bullet. What would lead to a length variation? Is it cheap bullets (I'm using bulk no-name brand bullets)? Or did I do something else I shouldn't have?


Of course, it is entirely possible that I am being too anal on this!!! I just measured a strand of my hair with the calipers, and that reads as .003 inches! So, we really aren't talking about a heck of a lot of variation here... But, you guys are my experts on precision, so what do you think?


Anyway, I'm still happy to have completed the process to some functional degree... Here is my first ten of fifty rounds:

http://i126.photobucket.com/albums/p85/coloradocop/randomstuff5-1041.jpg

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Bullet
May 8, 2008, 04:47 AM
If your are measuring COAL to the bullet tip you will get variations due to the bullets varying in length. If you measure from the bullet Ogive the measurements will be more consistent. I use this bullet comparator to measure on the Ogive -

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&item=09-600&type=store

The COAL length is important if you cartridges are going to be fed from a mag (they all have to fit in the mag) but somewhere on the Ogive will contact the lands not the bullet tip (this is important when seating longer than mag length/long enough to reach the lands).
Your (seating die [1]) doesn't seat the bullet from the tip but from somewhere on the Ogive and probably not from the same part of the Ogive as the (comparator [2]) measures from and not the part of the bullet that will contact the (lands [3]) either. All 3 will probably contact the bullet in different places on the Ogive, because all 3 are probably different diameters.

Here is a link that explains how a comparator works -

http://www.thehighroad.org/showthread.php?t=213082&highlight=comparator


.

coloradokevin
May 8, 2008, 06:26 AM
Thanks bullet! I was measuring from tip-to-tail, so perhaps that was my issue.

Just for clarity sake: if I am reading you correctly, my effective COAL may in fact be consistent, but it might just be that my bullet length is not? Is that pretty much what I'm getting out of this?

And, my wife says to tell you that you won't be on her Christmas card list this year, thanks to you talking me into buying another toy :)

Bullet
May 8, 2008, 10:21 AM
Just for clarity sake: if I am reading you correctly, my effective COAL may in fact be consistent, but it might just be that my bullet length is not? Is that pretty much what I'm getting out of this?

Yes, the length to the Ogive is probably more consistent. This is why your seating die doesn’t seat from the tip of the bullet. The bullet tips are probably where the variation is coming from.

ReloaderFred
May 8, 2008, 11:05 AM
If you'll measure the actual length of several of your bullets, you'll find there is variation in length between them. This is natural and part of the process of mass production. They set parameters for diameter, weight and length, and as long as the bullets fall within those parameters, then they're good to go.

Hope this helps.

Fred

strat81
May 8, 2008, 11:28 AM
Variation in bullet length isn't limited to bulk bullets either. Even some of the pricey stuff like Sierra Match Kings can have some variation.

I've heard that serious benchrest shooters weigh cases, weigh bullets, and measure bullets and group the closest ones together.

coloradokevin
May 8, 2008, 02:53 PM
It is kind of funny, after getting into reloading you learn so much more than you thought you ever needed to know about each component in a single cartridge!

I've been shooting for at least twenty years, and I never even knew the term "ogive" until probably a month ago. It just wasn't critical to my needs until recently!

Thanks again for the help guys!

cougar1717
May 8, 2008, 03:13 PM
.004 or .005 variation in COL is a very average range if you don't have a bullet comparator. To put that measurement in perspective, measure the COL of a box of some factory ammo.

rcmodel
May 8, 2008, 03:22 PM
+1
OAL length variation in factory ammo is sometimes enough to scare you!

rcmodel

ReloaderFred
May 8, 2008, 03:30 PM
Cartridge Over All Length is way over rated. What actually affects accuracy is where the bullet contacts the rifling in this regard, along with total bearing surface, pressure, burn rate of the powder, etc. It's the point on the ogive that meets the friction points of the barrel that is important.

As long as the total length of the loaded cartridge doesn't interfere with clearance in a magazine, or feeding, it isn't that critical. Again, it's the point of contact with the barrel, and the offset from that point of contact, that are important.

Hope this helps.

Fred

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