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 Twist rates and the AR-15 
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Location: Duvall
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Real Name: David
I'm looking at building a rifle with one of my new lowers. PSA has pretty much exactly what I want on sale today:

PSA 16" MID-LENGTH 5.56 NATO 1/7 NITRIDE MOE DISSIPATOR RIFLE KIT, OLIVE DRAB GREEN

My question is this. The 1:7 twist rate is designed to stabilize heavier bullets like up to about 80 grains. I've read conflicting viewpoints on how well it'll stabilize 55 grain plinking ammo (which is what I've got lots of). Some say you want a slower twist rate so you don't over-stabilize the bullet, while others say it's difficult to over-stabilize and the US Military has settled on the 1:7 twist rate barrel so why shouldn't you?

Thoughts?

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Thu Apr 27, 2017 2:31 pm
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Location: Central FL
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My ARs are 1:7 because that's a good all around twist rate. It stabilizes both 55gr and heavier 62/77gr well.

A slower rate might make for better 55gr accuracy at the sacrifice of 62gr accuracy.


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Thu Apr 27, 2017 2:52 pm
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Location: Lacey
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My 20' black hole barrel will put up sub 1/2' groups all day long no with 70gr -80gr it loves the 75-77gr. But barely puts up 1moa with the 62gr and the 55gr shoots minute of paper target lol (somewhere around 14'moa).

Every rifle is diff but this is my experience.


Thu Apr 27, 2017 4:27 pm
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Location: Puyallup/South Hill
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Real Name: Ryan
I have a 1/7 nitride mid Length set up from PSA and it shoots 55-68 just fine. Very reliable with better than average accuracy.


Thu Apr 27, 2017 4:58 pm
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Location: Faxon, OK
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Go in the middle with a 1:8 twist?

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Thu Apr 27, 2017 5:05 pm
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Location: Duvall
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golddigger14s wrote:
Go in the middle with a 1:8 twist?


Well, the sale is for a package deal with the 1:7 barrel.

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Thu Apr 27, 2017 5:07 pm
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Location: Bellingham Canada
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I am in the 1:8 club

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Thu Apr 27, 2017 5:18 pm
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Location: Everett
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My 1:9 chrome lined m&p barrel is my most accurate. But all I shoot is 55gr. I have a 1:8 & a 1:7.


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Thu Apr 27, 2017 5:45 pm
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Crap, or not. I waited too long and now it's out of stock. Oh well, PSA cycles through their sales fast enough, it'll come back around.

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Thu Apr 27, 2017 6:15 pm
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Location: south 'merca
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For plinking and range fun it's fine. I get shitty groups out of my 1/7 with 55 grain. Decent with 62 grain(1"ish) groups, and she's a tac driver with 69-77 grain. I'm rolling 75gr hpbt's and have been very satisfied

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Thu Apr 27, 2017 6:17 pm
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Acpguy wrote:
My 20' black hole barrel will put up sub 1/2' groups all day long no with 70gr -80gr it loves the 75-77gr. But barely puts up 1moa with the 62gr and the 55gr shoots minute of paper target lol (somewhere around 14'moa).

Every rifle is diff but this is my experience.


Do you mount your 20' black hole barrel to a wheeled or tracked vehicle?

;)


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Thu Apr 27, 2017 7:00 pm
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This story has been told a lot...

1:7 is the military spec b/c of the 5.56 tracer, which is really long...longer than any jacketed lead 77-80gr is going to be. Long bullets need a faster twist to stabilize. At some point, you can't stabilize and have to go the fin stabilized sabot/smoothbore route. Never heard of a civilian arm that needed to do that, though.

Military wanted 1:9 or 1:8 but needed 1:7. I have two 1:8 20" guns that shoot great, but I don't demand cloverleafs at 100 yards like some guys do.

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Thu Apr 27, 2017 7:57 pm
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Location: Lynnwood/Bothell
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1:7 is just fine. Shoot the lighter, cheaper bullets when pinpoint accuracy isn't required; when it is, just step up to heavier bullets.


Thu Apr 27, 2017 8:42 pm
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Location: Snohomish
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My FS2000, Tavor, Daniel Defense pencil, Spikes LE and 2 PSA barrels are 1:7. Have a few 1:8 and 1:9 as well. Honestly, i dont chase groups though so depending what you want. The way i shoot them with my purpose, havent been able to tell the difference.

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Thu Apr 27, 2017 8:53 pm
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Location: Tri -Cities
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1:9 is the way to go for 55gr. My 1:8 18" shoots 2" groups at 100yds with 55gr. With 69gr match (Prvi mind you), I'm hitting 1" groups at 300yds. Hard to find good barrels in 1:9 longer than 16" though.

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Thu Apr 27, 2017 10:59 pm
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