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View Full Version : 1:9 or 1:7 twist?????


Dirty506
09-24-2010, 12:33 AM
so i know what i want in an upper reciever all except what twist rate i want. i want a barrel that will last a long time and is very durable that would be able to handle the 55gr as well as the slighty heavier 62gr 5.56 rounds. now i know the 1:7 is for the heavier grains and is more accurate but i have also heard it wears down quicker as well but it is still has a decent lifespan. now the 1:9 isnt as rough on the barrel so i've heard and still catches the lighter grained stuff as well but isnt as good with heavier grains. which would you guys recommend? i trust you cal gunners and dont mean to be annoying i just want my AR to be built the right way for my uses.

DarthSean
09-24-2010, 12:40 AM
Either a 1:9 or a 1:8 twist will do fine for a 62gr. bullet. You don't HAVE to have a 1:8 unless you are going to shoot anything heavier and you don't NEED a 1:7 barrel unless you shoot 80gr. or heavier bullets, which are only used for matches.

Dirty506
09-24-2010, 12:56 AM
thanks man appreciate it

Cokebottle
09-24-2010, 1:00 AM
+1

1/9 really is the most flexible.
It'll stabilize pretty much anything any of us are going to run at the range, hunting, or SHTF, and it won't spin the jacket off of the lighter 55gr as 1/7 has been known to do.

killshot44
09-24-2010, 1:05 AM
The faster twist rates are meant to stabilize longer bullets. Since longer usually also means heavier (but not always)
a faster twist rate is known to handle long VLD and 80+ grain match/target bullets.

The 1/7 twist is "mil-spec" given the unusual length of tracer bullets. They've also used it successfully with the newish 77gr 5.56 rounds.

Many match barrels use a 1/8 twist rate which work extremely well with the long Berger & JLK VLDs of 80gr-90gr.

A 1/9 twist in a Stainless or Chrome-lined barrel should work well with anything up to 70gr.

I just sold a 20" HBAR 1/9 that was really good with 69gr SMK handloads. For general use my choice is a 1/9.

Dirty506
09-24-2010, 1:08 AM
i appreciate it and one more question which is better a chrome moly or chrome lined barrel?

U5512
09-24-2010, 1:56 AM
Chrome lined chamber and bore are preferred.

Rogu3
09-24-2010, 2:30 AM
Spin the jacket off? Doubt it...proof?

goodlookin1
09-24-2010, 6:50 AM
i appreciate it and one more question which is better a chrome moly or chrome lined barrel?

Do you care more for accuracy, or would you rather have an easier-to-clean barrel and longer lifespan?

If accuracy, then SS or Chrome Moly.

If ease of cleaning and longer life, then Chrome Lined.


I've heard it said that if the people doing the Chrome Lining really know what they are doing and are good at it, then it can be as accurate as Chrome Lined. I cannot verify this tho....it's just a general rule of thumb: You're probably not going to get match grade accuracy out of a Chrome Lined barrel. That said, you can still get 1 MOA and sometimes better with a Chrome Lined barrel.

YMMV.

Nathan Krynn
09-24-2010, 6:57 AM
I agree with most on this that a 1:9 is the most versatile. You really do not need a 1:7. Also I have a lot of 1:8's and love them.

I like chrome molly better then stainless by far. From what I am told by barrel makers stainless is easier to cut perfect holes and rifling as it is a more consistent blend of metals then molly but molly's leads last longer and that is the part of the barrel that wears out. So I like molly overall.

Chrome lining is easier to clean, makes the barrel last a little longer, prevents a lot of pitting and rust, but decreases accuracy as chrome can not be applied consistently down the bore. Depending on who did the chrome lining the accuracy loss could be not noticeable at all like null or 1/4 MOA, or I have seen as bad as 1-2 MOA, from barrels out of the same lot. Over all as long as this isn't my hunting gun or target gun, I chrome line it.

If you really want an awesome barrel then Melinite or salt-bath nitriding as it is called as well is truly the way to go. It is not a coating it penetrates the pores of the barrels and makes them harder and the the leads last like 20k-30k rounds, and the barrel comes out black and doesn't chip or wear.

goodlookin1
09-24-2010, 7:29 AM
If you really want an awesome barrel then Melinite or salt-bath nitriding as it is called as well is truly the way to go. It is not a coating it penetrates the pores of the barrels and makes them harder and the the leads last like 20k-30k rounds, and the barrel comes out black and doesn't chip or wear.

I've seen an upper that had less than 1000 rounds before with this nitride coating and when you clean it, it had a rough patch in the bore about halfway down the barrel where it had worn out or something went wrong with it. Needless to say, the accuracy suffered. I would never purchase another one of those "chrome lined" substitute barrels.....I think it's a gimmick because none of the manufacturers can prove it actually does anything; it's all just talk from what I understand.

YMMV.

Nathan Krynn
09-24-2010, 7:53 AM
It makes the metal extremely hard so if their is any burs in the rifling then they are basically permanent and the barrel is ruined.

ocabj
09-24-2010, 8:14 AM
I have no idea why people think 1:9 is more versatile than 1:7.

1:7 will shoot anything. 1:9 can't shoot 75 and up (people will try to argue 75gr A-Max will work, but that's iffy at best and is a YMMV) because it can't stabilize the heavier weights.

Spinning jackets off with 1:7? I've never put much effort in trying to, but I've shot 40gr factory varmint loads out of a 20" 1:7 and they worked fine. I'm sure if I tried to hotrod a handload with a 40gr or lighter, I could probably do it.

You're more likely to shoot a 75gr or heavier ammo than you are to shoot ammo lighter than 50gr, anyway.

If you want versatility, go 1:8 or 1:7. If all you want to do is shoot short range (200 yards and under), then stick to 1:9 and shoot the light bullets.

technique
09-24-2010, 8:41 AM
I've purchased a couple of ar's, one of which is an HBAR match upper with a 1:7..

what information do I need to determine the maximum bullet weight (length) I can feed it?

thanks..

First hand experience is what you'll need.
Buy some varying weights and shoot em. See what it likes, so long as it's acceptable accuracy to you, and puts round holes in the target, I'd say you're GTG.

My particular 1:7 ranges from 50gr-100gr.

3GunFunShooter
09-24-2010, 9:05 AM
I run a 1:8 which works great for 55 gr up to 150 yds. 77gr for anything longer distance.
JP stainless 18".

technique
09-24-2010, 9:08 AM
That's an interesting question.

No matter what, they can only be so long (OAL case and all) or they wont feed or fit in a mag.

Usually the heavier longer bullets are just seated in the case deeper. Throating is for extreme stuff, and machineguns.

What you have there, is ammo loaded with a heavy-for-caliber bullet, loaded long to allow for powder space. With a normal .223 chambered rifle, the cartridge would not fit due to the long bullet, and at best, would load with the bullet into the leade, thereby raising pressures. With a normal chamber, stick with the match loads with lighter bullets. Hope that helps.

Best description I could find.

ocabj
09-24-2010, 10:06 AM
I've seen ammo listed for "throated" only.. etc..

This is typically ammo with 80gr bullets (and 75gr VLD) where the ammo won't be magazine length, anyway. This type of ammo (e.g. Federal Gold Medal 80gr) is meant for use at mid-range (500-600 yards) to long-range (800-1000).

ocabj
09-24-2010, 10:27 AM
ahaa.. so it's not so much breech clearance but magazine length regarding feeding..

No, it's still about making sure it chambers without jamming into the lands at a dangerous depth.

I was just mentioning that the so-called 'match throated' ammo is easy to spot because it won't be magazine length.

killshot44
09-24-2010, 10:32 AM
No matter what, they can only be so long (OAL case and all) or they wont feed or fit in a mag.


Tech, that's no big deal. None of my best LR handloads will ever fit into a magazine. Bob-Sledô 'em. ;)

DavidRSA
09-24-2010, 11:05 AM
This thread came up at just the right time..

I have a stockpile of a few thousand PMC .223 55 gr AND a new BCM upper on the way with a 1:7 barrel.

What is the general consensus... its fine to use the 55gr in the 1:7 or it will "spin" the jacket off?

Mute
09-24-2010, 11:16 AM
I don't know where people are getting this spin the jacket off stuff. In all the time I've shot and seen people shoot 1/7 twist barrels on ARs, I have never, ever, seen a jacket get spun off a 55 grain bullet.

ocabj
09-24-2010, 11:17 AM
What is the general consensus... its fine to use the 55gr in the 1:7 or it will "spin" the jacket off?

It's fine. The military was using 55gr (M193) for a long, long time with 1:7.

ZX-10R
09-24-2010, 11:29 AM
1:7 you are good.

xxINKxx
09-24-2010, 11:38 AM
I dont notice any difference when shooting at the range, or desert with standard 55gr 223 out of either of my 1:9 and 1:7 twist uppers

Crawfish141
09-24-2010, 12:04 PM
I prefer 1:7 simply because it's milspec, and that tends to indicate a nicer quality barrel. However, I've never had problems with 1:9.

ArkinDomino
09-24-2010, 12:28 PM
I recently started using heavier bullets so i was glad i had a 1/7

Helpful_Cub
09-24-2010, 1:08 PM
You may also want to consider your quieter options. A 70 grain sub-sonic round carries a lot more energy than a 55 grain sub-sonic round. Granted, neither will go very far, but having the option in a SHTF situation is nice to have. Heavy bullet + right barrel + silencer + right ammo = quiet solution.

Keep in mind, this is for a special situation because you won't want hollow points at these lower velocities. But when combined with a silencer, your bolt sliding around should be the nosiest part of shooting your gun.

killshot44
09-24-2010, 2:49 PM
I prefer 1:7 simply because it's milspec, and that tends to indicate a nicer quality barrel.

http://i878.photobucket.com/albums/ab348/Killshot44_bucket/epicfail.jpg?t=1285364884

Crawfish141
09-24-2010, 2:59 PM
http://i878.photobucket.com/albums/ab348/Killshot44_bucket/epicfail.jpg?t=1285364884

How so? How many higher end barrels come in 1:9? Not nearly as many as there are in 1:7. 1:7 is not the causation of the quality, but it certainly correlates with quality.

Now if you're varmint hunting or some such a lighter twist is certainly more desirable. However, for that I'd prefer a slower twist rate either 1:12 or 1:14.

Cokebottle
09-24-2010, 4:01 PM
Spin the jacket off? Doubt it...proof?
That's what I used to say.

Couple of weeks ago one of the guys here posted a shot of his target.
One shot, the target had one clear bullet hole near the center, and a half dozen or so "rips" all around it.

Cokebottle
09-24-2010, 4:07 PM
It's fine. The military was using 55gr (M193) for a long, long time with 1:7.
The original M16 was a 1:12 twist.

When did the military switch to the heavier ammo relative to when they move to the 1:7?

Cokebottle
09-24-2010, 4:13 PM
How so? How many higher end barrels come in 1:9? Not nearly as many as there are in 1:7. 1:7 is not the causation of the quality, but it certainly correlates with quality.

Now if you're varmint hunting or some such a lighter twist is certainly more desirable. However, for that I'd prefer a slower twist rate either 1:12 or 1:14.
It doesn't correlate to quality at all.

It correlates to what the customers are asking for (regardless if they know what they SHOULD be asking for or not) and what manufacturers are used to making.

Most customers use logic similar to yours... military uses 1:7, therefore, I want to use 1:7.
If someone who was a "respected expert" on Arfcom decided that he was going to troll and started persuading people that 1:4 was better for "all of these reasons"... you'd soon see manufacturers start to offer 1:4 to meet the demand.

It happens that most of the high-quality producers are still making 1:7, but that doesn't mean that a 1:7 is going to be a higher quality.
YHM produces both 1:7 and 1:9.
RRA produces 1:9
The Ruger SR556 is 1:9

I'd take an RRA or Ruger 1:9 before a YHM 1:7.

SixPointEight
09-24-2010, 4:15 PM
That's what I used to say.

Couple of weeks ago one of the guys here posted a shot of his target.
One shot, the target had one clear bullet hole near the center, and a half dozen or so "rips" all around it.


Cokebottle's right. It doesn't happen all the time, but it HAS happened:
http://www.informaworld.com/ampp/image?path=/790627369/919471975/ufpm_a_461622_o_f0012g.png

Tom5390
09-24-2010, 4:20 PM
The term "milspec" that everyone in the AR world likes to throw around sounds like its the best in manufacturing specifications. But the term milspec actually means the lowest standard the military is willing to accept.

Some, (not all by any means) after market AR items actually exceed milspecs, so take the term "milspec" with a grain of salt. Milspec simply means it's meets the military's lowest acceptable standards, which BTW is not always the best in every comparison.

Cokebottle
09-24-2010, 4:26 PM
"Milspec" is simply a marketing term at the retail level.
It sells a LOT of crap.

ocabj
09-24-2010, 4:51 PM
Again, 1:7 for *versatility*. It will consume and shoot basically everything. 1:9 won't.

If you want maximum accuracy with the midrange 55-62, then I guess you can stick to 1:9, but that's not basing the decision on versatility. It's basing it on a decision to shoot a very specific ammo weight range.

I've heard people regret buying 1:9 because they wanted to shoot 77gr BTHP ammo. I've never heard anyone regret buying 1:7 because they wanted to shoot 40gr varmint ammo (which a 1:7 would shoot anyway, just not optimally).

maxima
09-24-2010, 5:39 PM
The main reason military adopted 1:7 barrel is they want to stabilize M856 tracer rounds. If you need that function, go with 1:7. Otherwise, 1:9 barrel is more than enough for 40gr - 75gr bullet.

JTROKS
09-24-2010, 6:09 PM
If you use light varmint bullets and shot at max load through a 1/7 twist it is possible to have the jacket break apart. Loading it down to 2700 fps should alleviate the jacket break up. I've learned that you can get very good accuracy with 55 grain bullets shot through a 1/7 twist barrel as long as you're not pushing the bullet too fast. My Colt HBar has a 1/7 twist barrel and it loves 77 grain SMKs. My Stag Varmint has a 1/8 and will shoot 55 grain bullets with better accuracy than my Colt HBar.

Dreaded Claymore
09-25-2010, 12:33 PM
From this thread, it sounds like 1/8 would be best if you're not shooting tracers.

DougJ
09-25-2010, 5:47 PM
I keep wanting to regret buying a 1:7 barrel because I'm reloading and most bulk bullets (no steel) are 55 grain. That's right at the bottom of what I feel comfortable shooting through that barrel.

It's not been an issue at all so far, but a 1:9 might be a better choice if 55 and 62 grain was all you're going to shoot.

hawk81
09-25-2010, 5:58 PM
Get a 1:8 barrel. It is the best of both worlds.

Capt. Speirs
09-25-2010, 6:54 PM
Chrome lined chamber and bore are preferred.

Why?

mecam
09-25-2010, 7:08 PM
I have over 1k rds of 55gr on my White Oak 18" 1/7 twist barrel and never seen a bullet shred to pieces. I shoot both a Hornady 55gr Spire Point chronoed at 2989 fps avg. and a Hornady 55gr FMJ chronoed at 2963 fps avg. Never had accuracy issues hitting 4" clay birds at 200yds.

-

Cokebottle
09-25-2010, 8:13 PM
Why?
More forgiving of improper care and storage ;)

ParallaxTactical.com
09-27-2010, 4:02 AM
416 Stainless Steel, 1:8. :)