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Old November 6, 2013, 01:49 PM   #1
rebs
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OAL for an AR ?

I have two AR 15's one with a 16" 1 in 8 barrel and one with a 20" 1 in 9 barrel. I was reloading different bullets to different OAL according to the bullet manufacturers. Then I decided to load them all to 2.255 and was surprised to find they all shot better with the longer OAL.
Has anyone else found this to be the case with your OAL ?
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Old November 6, 2013, 02:09 PM   #2
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Not always. With blunt nosed soft points (like the 70gr Speer SP) when I started getting near 2.230" I started running into feeding issues. I have achieved excellent accuracy with all my loads (3/4 MOA) and have not needed to try to seat longer out. With 55 gr Hornady SP (w/ cannelure) I seat to 2.195" and it also starts to have feeding issues if I start seating it extra long.
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Old November 6, 2013, 02:12 PM   #3
rebs
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I have not had a feeding issue with either of my AR's
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Old November 6, 2013, 02:25 PM   #4
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Most cartridges shoot most accurate with the longest OAL the chamber will allow. That reduced the amount of bullet tip as they enter the rifling. The further they jump to the rifling, the greater chance they'll enter a bit tipped. That slightly deforms them and too much deformation degrades accuracy.

It's easily seen if one makes ammo good enough and shoots it in rifles good enough to see the difference. Many competitors loading rounds one at a time "chase the leade" seating bullets out far enough to just touch the lands when chambered. OAL has to increase as the rifling erodes away.
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Old November 6, 2013, 02:28 PM   #5
Unclenick
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Rebs,

You're probably not shooting a blunt bullet shape, so you can seat longer without feed problems.

There are no guaranteed magic COL's. Bart's right about the trend for common tangent ogive shapes, but you just have to experiment with finding with each bullet and chamber combination to be sure. Berger's procedure for VLD shaped bullets will do OK for most bullets if you use the smaller change number per step.
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Old November 6, 2013, 02:30 PM   #6
mdmtj
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With the AR I load to fit the magazine. I haven't found that going any shorter helps any. Obviously I can't go any longer and still feed from a magazine.
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Old November 6, 2013, 02:42 PM   #7
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Have to be careful because there are several different AR chamber configurations available with differing freebore lengths. The same things may not be true for them all.

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Old November 6, 2013, 03:34 PM   #8
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Quote:
Have to be careful because there are several different AR chamber configurations available with differing freebore lengths. The same things may not be true for them all.
Very true. I've settled on one primary bullet for the ARs and it's a hollow point with a nice pointed nose. I've verified I'm clear of the lands with the OAL that fits my magazines.
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Old November 6, 2013, 03:58 PM   #9
rebs
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all the bullets I load for my AR's are pointed tips. Hornady soft point, Hornady FMJBT, Varmint extreme and varmint hollow point from Mid South Shooters. Also a Hornady 68 gr bthp. They are all pointed bullets.
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