243 AI vs 260 AI vs AR10 mag length

Hellbender

Gunny Sergeant
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Apr 23, 2008
1,560
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Lebanon, Missouri
I'm getting ready to build an AR10, either in .243 AI or .260 AI

With magazine constraints realized, which cartridge can I use the highest BC bullet vs velocity without using up all my powder space?

Will the 243 107-115's work at mag length with good velocity?

Or will a 139-142 gr. 260 be better?

Or will the ogive length not allow any of them to work?

Thanks,
HB
 

c ward

Gunny Sergeant
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Sep 23, 2005
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Denver Co.
Re: 243 AI vs 260 AI vs AR10 mag length

AI cases don't stack so well in 2 column double feed mags , probably better of with a straight 243 , 260 in a gas gun .

The straighter walls of the Ackley cases change the way the case lays in the mag . Have not tried this in AR10 mags but have in the AW mags which are double feed also and after 2 or 3 rds the mag wouldn't hold the rounds .
May want to try some dummy rounds first before committing to a custom barrel .
 

Hellbender

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Apr 23, 2008
1,560
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Lebanon, Missouri
Re: 243 AI vs 260 AI vs AR10 mag length

Thanks guys, looks like a plain .260 is gonna be hard to beat.

Time to call Mr. Krieger!

HB
 

ChadTRG42

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Jan 22, 2007
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www.dallasreloads.com
Re: 243 AI vs 260 AI vs AR10 mag length

HB, I would also avoid the AI in a gas gun. For bullets, it's best to use a non VLD type in a gas gun. Use like a 142 SMK, 139 Scenar, Bergers 140 BTHP (non VLD). If you want more speed, look at the 120 grainers- 120 A-max, etc. 260 gets my vote. But a 243 is nice, as well as a 7mm-08. But, a 308 in a gas gun is very nice!