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Case length and COL


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#1 Yateswell

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Posted 18 May 2011 - 05:39 PM

I’m new to reloading and have been doing some reading and research. Recently the question of “right” case length and case overall length come across and I don’t know the answer to it, hopefully you experienced guys can shed some light on this.I’m reloading for my bolt action .223Rem rifle, I trim the case to 1.76” according the reloading manual and set the COL as long as possible that the bolt can close normally. I can now get sub 1” group at 100 yard. Am I doing the right way? Is there a better/accurate way to figure out the “correct” case length and COL for the gun I’m reloading for? Or is this something even worth worrying about?

#2 204destroyer

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Posted 18 May 2011 - 05:54 PM

Thats the way I do the 204. Sounds correct to me.

#3 Desert Fox

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Posted 18 May 2011 - 06:03 PM

COAL - Cartridge Over all Length. This is the measurement from the base of the loaded case to the tip of the bullet.Case Length - This is an actual length measured from the base of the empty case to the tip of the neck. SAAMI has standardized the length of every cartridge that are on their list. Each case has a specific measurement for maximum and minimum length. If your measurement is above the maximum, the case had to be trimmed to spec.Cartridge Overall length can be dictated by the rifle magazine internal dimensions. You want to make sure that the loaded round will fit the magazine. Most rifle will shoot accurately with the bullet seated closer to the land... at least .010" off the land. VLD bullet like' it much closer...sometimes even kissing or touching the land. Your rifle will tell you.
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#4 Bisley

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Posted 18 May 2011 - 06:52 PM

I’m reloading for my bolt action .223Rem rifle, I trim the case to 1.76” according the reloading manual and set the COL as long as possible that the bolt can close normally. I can now get sub 1” group at 100 yard. Am I doing the right way? Is there a better/accurate way to figure out the “correct” case length and COL for the gun I’m reloading for? Or is this something even worth worrying about?

Yes and yes. Yes, that way will work, BUT yes, there is a much better way. http://www.midwayusa...ctNumber=231904http://www.midwayusa...ctNumber=570611Hornady (and I'm sure other manufacturers) actually make tools just for checking your overall length. I myself do not use the modified case and tool designed to push a particular bullet into the lands to be measured. I make a dummy case myself (I can be so cheap sometimes) by removing part of the neck to allow the bullet in question to slide back easily when the bolt is closed. You do this several times and you will have an excellent "base" measurement. Then I usually subtract about .010 since I hunt and want to make sure they function. I do however love the caliber specific collet tool that clamps onto your micrometer to measure the bullet at the olgive and not the tip where it may be deformed. It may sound kind of different reading about these tools, but when you look at them, you will see how very simply they work.

#5 tawnoper

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Posted 19 May 2011 - 06:42 AM

For a guy just getting into it, I'd stay with what your manual states until you start understanding things a bit better. For a .223 the max length is 1.760"...you can trim to 1.750" and it should last a few firings before needing trimming. As for overall length I'd seat the bullets out far enough that they fit your magazine. For a single shot I'd start with manual length or for a 50/55 grain bullet, at least seat them one bullet dia deep.
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#6 Frank

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Posted 19 May 2011 - 06:50 AM

and set the COL as long as possible that the bolt can close normally.

Yates, sometimes you have to be careful with that method, especially is used for hunting. If you have a round in the chamber and decide to unload the gun, the bullet can actually get stuck in the lands & come completely apart, spilling powder everywhere. And if a long ways from the truck, you are done hunting. Not that has ever happened to me before. :smiley-funny-post-sign: There are several methods of arriving at COL, and NONE seem to bring EXACT measurements for me. The Stoney Point tool comes close, which is what I use, but requires the patience of Job(e). It too is a pain in the a_ _, as you have to take r e p e a t e d measurements to get almost close. Of course if one does this about one bazillion times, the better one will get at it... and if one has L-O-T-S of time on their hands. Some will put a bullet in an unloaded, already fired brass and close the bolt. This is a very inconsistent & unreliable method IMO. As mentioned above, making sure the rounds FIT in the magazine is important and can be easily missed. Folks will be so intent on getting that max COL & then go to the range without checking if they fit in the magazine, which sometimes the rounds will not. A big problem if using that rig for hunting of course. Another possibility, is to compare your longest loaded rounds (at the range) to an industry standard COL round, found in the loading manuals. Sometimes the longer rounds are no more accurate. The "book" COL can be a good starting point in other words, especially for the lighter bullets in any given caliber. :sport037fn4: Frank

#7 Frank

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Posted 19 May 2011 - 06:51 AM

oops... tawnoper beat me to it... LOL but great advice IMO

#8 oz_fox_hunter

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Posted 19 May 2011 - 07:51 AM

I'm a stickler for keeping to what's in the bullet manufacturers manual. :smiley-funny-post-sign:

#9 Baja_Traveler

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Posted 19 May 2011 - 11:37 AM

If you want to really know what your rifles chamber dimensions are, and the corresponding COL of the ammunition to fit it, you need to make a chamber cast. I just finished making an impact impression of my Sharps chamber and throat, so I can have a custom bullet mold cut for it. The dimensions I got off the impression tell me exactly how long my case length should be for my particular rifle, how far the jump is to the lands and what is the proper bullet diameter I should be casting. With that information you can reliably custom make your ammunition for maximum accuracy out of your individual rifle. HERE is an excellent article of the various methods of obtaining chamber dimensions.

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#10 Caneman

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Posted 23 May 2011 - 10:21 AM

Posted ImagePosted Image

#11 Leonten

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Posted 14 October 2011 - 11:01 AM

I have to challenge the Desert Fox's reply. The Hornady diagram above shows a perfect example. You have to trim the cartridge to fit the chamber, not the magazine. In the above picture you can clearly see that the case mouth is slightly shorter than the beginning of the freebore throat lead. If the case were too long (stretched too much) the chamber would actually cause the case to add more crimp to the bullet. The result would be higher pressure.

#12 Frank

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Posted 14 October 2011 - 03:13 PM

Leonten, that is not what Fox had said. May want to re-read the posts above.COAL = Cartridge Over All Length.... NOT just the "case" length.Fitting a cartridge to the chamber is a given. However, it is the MAGAZINE that rounds have to FIT in AND cycle without jamming. This is why sometimes cartridges cannot be loaded to it's chamber's longer length. This is a common problem that is often over looked, especially by begining handloaders.The above is referring to "hunting" rifles, and not tartget rifles that are normally loaded one round at a time directly into the chamber. Frank

#13 Desert Fox

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Posted 16 October 2011 - 06:42 AM

Leonten, that is not what Fox had said. May want to re-read the posts above.COAL = Cartridge Over All Length.... NOT just the "case" length.

Frank, Thanks for clarifying that.Leonten, Don't get confused between case length and Cartridge overall length. That'll drive you nuts. :signbummer8tl: Welcome to the forum brother.
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#14 240 supervarminter

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Posted 16 October 2011 - 10:20 AM

the easy way of doin it is hornady o.a.l gauge its 30.00 bucks or so.wait until u try some berger vld's......man what a pain getting those dialed!!!!!! goodluck once you figure your seating depth you should see some improvment on your groups.




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