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Old November 19, 2012, 07:17 AM   #1
rebs
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COL for an AR15 ?

How do you guys decide what COL to use ? Do use the magazine length for all bullets or go by the reloading book or work up your own for your particular rifle ? I have loaded a few 55 gr Vmax's at 2.160 and 2.250 and not seen a significant difference in accuracy, why not ?
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Old November 19, 2012, 07:58 AM   #2
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Seat at least one bullet diameter (.224) into the case, fits into the mag, seat to mid cannelure if bullet has one. I rarely if ever read the manual OAL.

Why not? Could be many things, the 223/5.56 AR has a long throat, anything seated to mag length will always have a long jump.

Of all the things that affect accuracy, OAL is way down on my list, especially in a 5.56 AR.
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Old November 19, 2012, 09:59 PM   #3
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Load as long as you can and still use your magazine with bullets designed for the magazine. AR's aren't generally too picky about COL, and if a bullet gets set back a little during the cycle, you built in some margin for error by doing your load workup with the bullet as long as you could seat it.

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Old November 20, 2012, 03:58 AM   #4
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I'm with the other guys, I don't break out the calipers or AR's or CZ 527's- just go by clip length and call it good.
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Old November 20, 2012, 05:52 AM   #5
rebs
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In the new Hornady loading book it says they used a Colt AR 15 as their test rifle, then they go on to say what col to use for their bullets. Like all the 55 gr loaded to 2.200 and 55 gr Vmax loaded to 2.250
Why do they put that in the book ?
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Old November 20, 2012, 08:18 AM   #6
steve4102
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Quote:
Why do they put that in the book ?
To tell the handloader what OAL was used during testing. Some manuals find this info unnecessary and do not list the OAL tested. They instruct the handloader to find the best OAL in Their rifle. Barnes for example suggests .050 off the lands for their bullets, can't find that in any manual. Nosler lists no tested OAL.

Here is what Accurate and Ramshot have to say about OAL.

It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a
guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of the barrel,
3) ogive or profile of the projectile and 4) position of cannelure or crimp groove.

Last edited by steve4102; November 20, 2012 at 08:30 AM.
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Old November 20, 2012, 10:34 AM   #7
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There is also often a SAAMI maximum overall cartridge length listed. To learn what I'm doing that's what I aim at with my caliper. When I've got more confidence, I'll get the extras and actually mesure and compare and (SAFELY) experiment.

As an addtional, if you check that Hornady book some more, you'll see they offer a .224 diameter bullet recipe that can NOT be loaded to magazine length, and must be loaded singly, and this is for extreme range benchrest/competition type shooting.
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Old November 20, 2012, 11:38 AM   #8
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Using Hornady 55 fmj bullets in two different manufacturers AR-15's to seat the 55 fmj to touch the lands overall length would be 2.370-2.390". At that length the bullet is just about to fall out of the case. In my .223 bolt action Remington the same Hornady 55 fmj bullet touches the lands of the barrel at only 2.246". The long throat of AR-15's makes it impossible to seat bullets close to the lands except for the 75-80-90 grain match bullets which are intended to be loaded into the chamber by hand and not from the magazine. So, follow manufacturers recommended overall length or to the 2.260" maximum magazine length. You won't gain much accuracy trying to seat bullets out to the maximum 2.260" magazine length so I'd keep them to recommended lengths or close in the AR.
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Old November 20, 2012, 12:27 PM   #9
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If you experiment with bullet seating depth you'll find accuracy sweet spots. It's not uncommon to find two, one further out near the lands, and one with the bullet seated deeper. Your best bet is to find whatever best accuracy seating depths you can identify, then use the one that is best for feed reliability if magazine fit and feed is what you are after.

Berger's method of finding best seating depths is here.
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