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So I ordered an AR-15, jees no will power. Anyhow it has the 16" barrel with 1 in 7" twist. It seems I remember reading somewhere that 1 in 7" should use +60 grain bullets?

Figured I would ask the experts on this forum what would be the more compatable ammo configurations to use.
 
Posts: 40 | Location: Minnesota | Registered: January 18, 2022Reply With QuoteReport This Post
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A 7 twist CAN shoot 60+ gr bullets.
It will stabilize anything lighter (shorter) but there is some risk of fragmenting a light varmint bullet. I know my 6.5 twist barrel will blow up a Hornady Amax in flight.

But you will be just fine with the usual 55 gr bullet. That was part of the spec, they had to be able to shoot leftover M193 ammo.
 
Posts: 3140 | Location: Florence, Alabama, USA | Registered: July 05, 2001Reply With QuoteReport This Post
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I use 62gr. M855 in my ARs with 1:7 and it works well.
I've also used the 55gr. and that worked also.
Try a few different rounds and see what you AR likes.


I'd rather be hated for who I am than loved for who I'm not.
 
Posts: 3569 | Location: The armpit of Ohio | Registered: August 18, 2013Reply With QuoteReport This Post
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A 1/7" barrel will allow you to shoot bullets with weights up to at least 77 grains under normal atmospheric conditions. You can also shoot bullets as light as are loaded in commercial ammunition.

For reasons having to do with spin rate and imperfections in the bullets, maximum precision is usually obtained with bullets that are spun no faster than necessary for stabilization based on their length, but unless you plan to take on the benchrest crowd, that should not be an important factor.

Most bullets intended for maximum precision from the 223 Remington cartridge are 69 grains and up, but that doesn’t mean you can’t shoot lighter bullets. On the other hand, the common M855 load with its 62 grain bullet has a poor reputation for precision in general, and that’s no doubt due to their construction as well as the fact that no one expects the load to perform at “match” levels. There is nothing magic about shooting heavier bullets just because they’re heavier.

For my semi-serious purposes and when I want best accuracy without going to top tier ammunition, I’ve found IMI 77 grain open tip ammunition to be reasonably good even in 1/8" twist barrels, and that might be getting to the edge of stabilization. Of course, shooting at high elevations helps avoid those problems.

Ultimately, though, the best load(s) will depend upon your rifle and your intended use of it.




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Posts: 46419 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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Yep, a 1 in 7 barrel should shoot most anything without issues. Some of the lighter, higher velocity varmint type bullets might not do so well. In some cases they can fragment in flight or (some claim, I've never seen a case of this) spin so fast that they de-stabilize and accuracy goes to pot. But any of the usual military weight ammo (I'm making that assumption, based on your use of "5.56" rather than ".223") should do fine.
 
Posts: 6796 | Location: Southern Idaho | Registered: February 12, 2007Reply With QuoteReport This Post
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Posts: 10526 | Location: Gilbert Arizona | Registered: March 21, 2013Reply With QuoteReport This Post
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Thanks for the info! I know that I only mentioned 5.56, but I would use eather 5.56 or .223. I have no preferance, partly dependent on priceing. My intentions for this gun is just for fun, not for competition and I certanly don't need match grade ammo.
 
Posts: 40 | Location: Minnesota | Registered: January 18, 2022Reply With QuoteReport This Post
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quote:

Similar to "The Chart" -- which put Colt AR15s on a pedestal for years -- this graphic should be taken with a large grain of salt. It's a good place to start, but it's not the final word.

My first AR15 had a 1:9 twist 16" barrel. Its most consistent accuracy was with 69 grain SMK bullets, and the best of that was with Federal GMM 69. If I really wanted to hit a target at hundreds of yards, FGMM 69 was the ticket. In warm summer temps, this barrel also performed very well with 75 and 77 grain match loads. The barrel's tightest group ever at 100 yards was with FGMM 77. But in winter, I limited ammo to 69 grains.

My 1:8 and 1:7.7 twist barrels are just accurate with any match ammo. 40, 50, 55, 69, 73, 75, 77 grains all shoot well with quality ammo.

My 1:7 twist barrel also did well with light ammo. Hornady 40 grain Vmax was great. Hornady 55 grain Vmax was outstanding. FGMM 69 was outstanding. And of course it did well with 73-77 grain loads.
 
Posts: 7505 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
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