How well will 1:7 stabilize 55grn?

[Smeh]

I'm looking at getting a new barrel for my AR15, and I'm wondering how well a barrel with 1:7 twist will stabilize 55grn bullets.

I tend to shoot a mixed variety of rounds up to about 62grn, but all the stainless barrels I find tend to be 1:7, rather than 1:8 or 1:9.

If I can find a 16 or 18 inch bead blasted stainless steel barrel with a 1:8 twist for $325 or less then that would make my day.

 

[Al LaVodka]

Never Give Up!

Never surrender!

People buying stainless barrels tend to be longer range, heavier bullet, target shooters. Hence 1:7. All I can say is: keep looking. If you are fairly confident you are not shooting much heavier than 62 grs. and may be shooting lighter... At LEAST 1:8. Better 1:9.

Now people will start telling you what the Army, set up primarily for NATO (62 to 77 gr. rounds), uses and that if its good enough for them...

Al

 

[Smeh]

I should mention that I shoot mostly 55grn, but would like to be able to shoot heavier and maintain the possibility to stabilize 55grn as well as possible.

 

[RyanM]

55 grain in a 1:7 is fine. It ends up a little overstabilized, and accuracy may drop a little bit compared to 1:9 (usually depends on the individual barrel), but that's about it.

 

[Howard Roark]

They will shoot fine. I use 55gr bullets for 100 yard practice in my service and match rifles, both have 1:7 barrels. I've shot thousands of them. Any primer and WCC844 powder.

 

[wanderinwalker]

What Mr. Roark said. I shoot 52gr HPBTs & 748 out of my 1-7" twist match barrel at 100 yards without issues.

Really, I think the idea of barrel twist affecting "optimum" accuracy with 55-62gr ball ammo is a bit much. As long as you have enough twist to stabilize them (ie, don't shoot 62s in a 1-12" barrel), they'll shoot as well as they shoot. IMO, it's not fair to indicted barrel twist rates when so much of the generic 55 and 62gr FMJ ammo just plain ol' can't shoot THAT well relatively.

 

[briansmithwins]

My ARs go from 1.5MOA with 75gr PPU to 2MOA with 55gr XM193.

1/7 chromed light weight barrels on both. BSW

 

[APIT50]

Depending on the barrel if you use thin jacket 55 grain bullets at higher velocities there is a chance of them coming apart upon leaving the barrel. 1-8 or 1-9 would be ideal for what you seem to be wanting.

Bravo Company and RRA both have what you are looking for.

 

[Al LaVodka]

Is that your selling point?! Those are both pretty poor performance IMHO.

And why knowingly lose half a MOA in accuracy? From an AR!? What's the rationale for that!?!?!? If you know you are not going to shoot heavier than 62 gr... Its like talking to Homer Simpson about this -- all I hear is people say what they do, don't know any better, but think that it is important and that there is no science behind ballistics. I just don't get it and should just shut up.

Al

 

[Smeh]

Therein lies the problem: I don't know if I'm going to shoot heavier than 62gr. It seems likely that I will at some point, so I'd like a barrel that will shoot the widest variety of standard loads today.

It seems to me that a 1:8 twist will do what I want the best. Am I correct in assuming that it's a good compromise between 1:7 and 1:9? If said twist rate will shoot well between 55gr and 77gr then I'd be willing to drop a bit more cash to get a barrel of my specification with 1:8.

I'm currently looking at Rainier Arms, Sabre, and White Oak barrels. Specifically this one:

http://www.rainierarms.com/?page=shop/detail&product_id=815

 

[RP88]

My chromed and 1:7 middie can keep 55gr .223 PMC around 2MOA.

 

[Al LaVodka]

55 gr. = 1:11 (was originally slower 1:12 and even 1:14 trialed). Up to 62. gr = 1:9.
Didn't someone explain that here already?
Al

 

[briansmithwins]

And why knowingly lose half a MOA in accuracy?

Because I save $100+ per thousand.

Most of the shooting I do is at matches where the targets can be 8" steel at 300 yards. 2MOA is plenty good enough for those. BSW

 

[wanderinwalker]

And why knowingly lose half a MOA in accuracy? From an AR!?

That 75gr PPU stuff is better bullets than the XM193 FMJ. I doubt the 1/2-MOA accuracy difference is entirely attributable to the "too fast" twist. I know a couple of Highpower shooters who use XM193 (or similar) at 200 yards offhand for our early-season shoots. I also know a few quite happy with the PPU out to 300 yards as well.

I have a new shooter's Highpower clinic (helping out the instruction) and a league match this weekend. I'll try to find some space in between to shoot some 52gr HPBTs at 100-yards from my "too fast" 1-7" twist and post the pics, alongside the 77gr ammo this twist is "ideal" for. I'll try to dig up some 55gr XM193 or similar for comparison too.

I still contend it's the quality of the AMMO more than the barrel twist rate.

SMEH: The 1-8" twist barrel is a good choice as well. It will stabilize 80gr Sierras (or VLDs) out to 600-yards, and supposedly they offer longer life than a 1-7". Of course, the 1-7" are supposed to offer increased accuracy with the 80s past 600-yards, from what I have read and heard.

 

[Bartholomew Roberts]

The Army tested 55gr from both 1:12 and 1:7 barrels and found no difference in dispersion out to 275yds.

And why knowingly lose half a MOA in accuracy? From an AR!? What's the rationale for that!?!?!?

You seem to be blaming the loss of accuracy the lighter bullet in the faster twist; but I bet it has more to do with M193 simply not being that great of a bullet ballistically or in terms of consistence. Load a nice match round like Black Hills 52gr Match and I bet the barrel would show the same accuracy as with the 75gr (or even better) - despite the 1:7 twist.

 

[Canuck-IL]

Am I correct in assuming that it's [1:8 is] a good compromise between 1:7 and 1:9?

Yep, it does seem to be approximately in the middle.

I have both a 1:7 and a 1:8 ... both do just fine up to 80s with the 7 just a hair better ... certainly a difference I can't hold well enough to matter.

Most 55s are marginal for accuracy ... there are some nice 52s that fly fine from the 1:7. I've never seen or heard a reliable report of a 55 coming apart due to 'over-stabilizing' spin rate - I think that fairly rare phenomenon is the domain of sub-50 grain, thin-skinned varmint pellets.

RRA has 1:8s and John at WOA can get you one altho the wait may be a bit as he usually stocks 1:7.
/Bryan

 

[Smeh]

I think I may postpone my purchase until after I see the results of your test, Walker. I'm very interested to see how well 1:7 stabilizes high quality 55gr bullets compared to 77gr.

 

[Zerodefect]

Should be ok at 100. But for longer ranges I'd recommend shooting better/heavier ammo anyway. Worst case senerio is your opening up your groups 1" at 100. Not a big deal, since you have to upgrade to real ammo if your after accuracy anyways.

I use 55gn for plinking only in my 1/7 AR. Usually close range tactical type practice. But at longer ranges or for defense I go up to 70+ grains.

 

[ole farmerbuck]

I have 4 .223's with 1:9 twist. They all shoot 40's up to 55's great. Havent tried anything heavier but i have some 69's i might try for the heck of it.

 

[Lloyd Smale]

Ive shot them in the 1-7 twist ar ive got. 55 ball doesnt shoot alot worse the the 60 grain ball does. With good comercial bullets i notice a bit more spread though. I would guess its more of a case that the jackets arent tough enough to handle the faster twist then it is a stabilization problem. Alot of the 52-55 grain bullets have very thin jackets to come apart at lower velocitys. If you do find you have a stabilization problem it will help alot if you just lower your velocity a couple hundred fps.

 

[wanderinwalker]

I think I may postpone my purchase until after I see the results of your test, Walker. I'm very interested to see how well 1:7 stabilizes high quality 55gr bullets compared to 77gr.

Smeh, you could buy with confidence now, 1-8" or 1-7". Not to spoil the suspense, but the 52s will fly into little knots at 100 yards. The 77s will also fly into little knots at 100, 200 and 300 and reasonably well at 600 on a calm day. It's the 55s that have me curious though. "High quality" and "55gr FMJ" just don't sit side-by-side in my mind is all.

I'll do my best to get some targets and pics this weekend though, just because I opened my mouth in the first place...

 

[rattletrap1970]

I have a Savage BTCSS in .223. It has a 1:9 stock stainless fluted heavy barrel. It absolutely will not stabilize anything under 69gr (with any powder or any loading I've tried).

 

[ole farmerbuck]

I have a Savage BTCSS in .223. It has a 1:9 stock stainless fluted heavy barrel. It absolutely will not stabilize anything under 69gr (with any powder or any loading I've tried).

Something doesnt seem right. My 1:9's love the 40's. AR's and bolts. (savage and stevens bolts)

 

[dom1104]

Yeah that does not sound right.


Part of the reason I go with 1/9s is I shoot 55 to 69 grain bullets primarily, as they are cheaper than the 75 to 77s here locally.

And, because every bolt gun I have seen is 1/9. for easy loading of ammo for both guns.

AND, primarily, because it shoots better with the 22lr conversion kit.

Which frankly I shoot more than anything else.

I cant say as I miss shooting the 75 to 77 grains, my targets dont know the difference.

 

[loadedround]

I have two Colt AR15's; one is a an HBar and the other is the Carbine both having 1/7 barrels. I bought both at very reasonable prices because brcause the orginal owners could not get them to group with either 55 gr GI or commercial ammo. One comment was it patterns like a shotgun. When I switched to either 62 or 69 gr bullets, both group at 1 MOA with Varget and I'm sure they both will do much better when I have the time to work on the load. Just my two cents worth.