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 Best gr. weight for 1/9 twist, 16in. barrel?
JimInMichigan  [Member]
4/8/2008 1:32:45 AM
Reading everyone loves TAP red box LE 5.56 nato in 75gr.
But also read here that 75gr best in 1/7 twist.

What should us 1/9 twist owners buy?
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ma96782  [Team Member]
4/8/2008 1:45:21 AM

Q. What twist rate do I want for my rifle?

Probably 1:9, but it depends on what kind of bullets you intend to shoot.

Special purpose rifles often have uncommon twist rates. For example, if you are building a varmint rifle and want to shoot the short 35 grain, 40 grain, and 50 grain bullets, a 1:12, or even 1:14 twist would be best. On the other hand, long range High Power shooters often select 1:8, 1:7.7, 1:7, or 1:6.5-twist barrels to stabilize the long 77, 80 and even 90 grain bullets used for 1,000 yard competition. Additionally, new testing of heavier rounds (68-77 grains) seems to show that they perform very well in simulated tissue and may be a better defensive choice than 55 grain or 62 grain rounds. The majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight.

1:12 twist rifles cannot stabilize SS-109/M855 bullets and 1:7 twist rifles are slightly less accurate with lighter bullets and will often blow apart the thin jackets of lightweight varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a significant amount of M856, the 1:9 twist rate is better suited for general use.

There is, of course, an exception: if you want to use loads utilizing the heavier, 75-77 grain match bullets currently used by Spec-Ops troops and other selected shooters, you'll want a 1:7 twist barrel. Although military loadings using these bullets are expensive and hard to get, some persistent folks have managed to obtain a supply, and will need the proper barrel twist to use them. Anyone who foresees a need to shoot this ammo should consider a 1:7 twist barrel.



Opinions (Pro and Con):

1:9 is best.
Why? Flexibility. It doesn't seem to have any problems throwing M856 tracers around, unless it gets really cold, it wears better than 1:7 and it stabilizes more rounds than 1:12. Additionally, 1:9 rifles, even Mil-Spec chrome chambered and barreled, can attain 1.0-2.0 MOA out to 300+ meters.

No, 1:7 and 1:8 are the best.
Why? Accuracy. For heavier and longer rounds during competition shooting, 1:8 and 1:7 twists are the best for heavy 77-80 grain rounds that I use to shoot competitively at 500-1000 meters. Who needs to shoot tracers anyhow? More importantly, heavier rounds are showing very good results in terminal testing and are proving to be much better defensive rounds.


Taken from the Ammo Oracle.

Aloha, Mark
FMJ  [Team Member]
4/8/2008 1:01:43 PM
Ive shot 77gr with no trouble in my 1/9 bushy


I like 1/7 twist myself
Ive shot 40gr to 77gr without trouble


mr_wilson  [Team Member]
4/8/2008 1:10:39 PM
Buy the heaviest weight round that your rifle shoots the "best".

(OP) - How will I know which that is?

YOU will have to determine what's best round for YOUR rifle, by buying a variety of factory or surplus ammunition and shooting them IN YOUR RIFLE.

Sorry, but IF you have read the Ammo Faq tacked above, then you have all the knowledge you need and simply need to get down to appling this knowledge to your rifle by testing various ammnution to see which performs best outta YOUR rifle.

mike
Cedric_MAC_19d13f  [Member]
4/14/2008 4:35:50 PM
Military shoots 62 grain, and i would recommend it. But if your just looking for ammo to plink with i would use just 55 grain, much cheaper.
qcka  [Life Member]
4/15/2008 3:13:21 AM
I'm not what you would call a precision shooter, so take this for what it's worth, but I ran 20 rounds of 75gr TAP through my 1:9 M&P15T last week. That was the most my wallet could justify these days

Shooting 5 shot groups at 100 yards with an Eotech, I was consistently w/in a 3" diameter circle. That's about the best I can do with my eyes and very slightly better than the 55gr PMC bronze I was shooting for the rest of the session.

I seem to be ok with the heavier load, but others have had more fliers. I would suggest trying out several types of ammo and finding what works best for your particular setup.

TehLlama42  [Member]
4/15/2008 9:05:54 PM
I'd try whatever you can get your hands on, although it seems that the TAP in 62gr should work.
Sill, for plinking, no reason not to try some 55gr and see how your rifle likes it.
Zhukov  [Moderator]
4/16/2008 10:50:34 AM
Ammo FAQ, entry #2
12_gauge  [Member]
4/16/2008 7:33:56 PM
Inside your house stability isn't an issue unless you will be firing across the length of your indoor Olympic pool room or something. Buy 75gr T2 for in the house. Out-doors, (read:250m+) I take a different stance than other people and am a fan of the 55gr+ ballistic tip type rounds after about 250 meterss or so. At that distance from a 16" tube they stop "blowing up" on soft targets, and you should see 12" or so of penetration easily with a nasty amount of fragments still in the wound-track. No barrier penetration is afforded though.

For an example, look at the SS197 round in gelatin from a 5.7 pistol. Remember, that is only a 40gr bullet, but it still gets 10-12" penetration ruitinely at the reduced velocity. Compare this to the SAME 40gr bullet in a .223 and it gets 5.5" penetration or so.

At distance on a soft-target, I think Nosler BT's are the bomb.

*flame suit on, but support your disagreement with fact if you do!*
norseman1  [Member]
4/16/2008 7:43:25 PM
Don't judge your barrel performance on crappy ammo.

Wolf (anything) is not known as sub MOA.

I would suggest 68gr Black hills blue box. I have had excellent results with it and my 1x9 barrels.
FMJ  [Team Member]
4/17/2008 12:44:49 PM

Originally Posted By norseman1:
Don't judge your barrel performance on crappy ammo.

Wolf (anything) is not known as sub MOA.

I would suggest 68gr Black hills blue box. I have had excellent results with it and my 1x9 barrels.


Wolf M193 and Wolf 75gr are very accurate
Battl3fr0nt  [Member]
5/5/2008 5:16:54 AM
ammo cost so much now it is just not worth getting a 1/7 unless you have a stockpile of 73gr.+ of ammo.. and you can shoot 77gr with a 1/9 twist just fine it is just not good untill you get past about 300M.. it will shoot not to bad at 100M maby 3" groups but once you get to about 600M-800M then you will notice it shooting just like a 1/7 match barrle.. it is weird how it works... but even then its like 40 bucks for even 69gr match ammo.. and the is the best you will get.. 69gr is just the right ammo for some reason... it will get you out to 800 easy and on target.. 62gr will do that to but wind will be a factor.. that is if you have a good barrle.. and 16"-20".. If ammo prices dont go down I will be shoot wolf 62 untill that goes up.. I would rather shoot 140-200 rounds at the range of not the best ammo then 20 -40 rounds of top ammo.. but yeah alot of match shooters use 1/9 twist and shoot just as good as the 1/7 guys.. if anything it is all about being a good shot and having an Acog

I see alot of people at the range shooting with scopes on there AR at 100 yards with 1/7 twist and not cheap scopes but I mean it would be somthing you put on a hunting rifle not an AR and they just suck.. most matches they have the open sights, acog then scope.. kinda thing going.. then agian some are mixed but most people just use an acog for long range.. I have seen them befor just have not got a chance to go to one.. but yeah 1/9 will shoot very well.. it is about the shooter and having good ammo.. not so much having 2 grain more then the other guy...
FMJ  [Team Member]
5/5/2008 7:23:38 AM
1/7 can do the same as 1/9


Ive shot win 40gr to 77gr

Both my LMT M4`s like the SMK 77gr the best of all
But I do use the BH75gr

Win 45gr shot nice and tight groups better than M193


1/7 can shoot 45gr bullets let alone 55gr
11BDad  [Member]
5/5/2008 9:11:15 AM
JimInMichigan,

Are you inquiring specifically about a TAP round or in general?

My 1:9 RRA will do 2moa (10 rds @100) with IMI M855 or LC XM855. Had several groups less than that with Prvi 75gr PPU Match. Haven't tried any 77gr.

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