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9/22/2017 12:11:25 AM
Posted: 9/7/2005 5:50:51 PM EDT
I have read the Ammo Oracle several times.....I have run searches here many, many times....and I have talked to lots of shooters at my local range................and I still don't think I have a good definitive answer.

So, once again, I have come to you gentlemen, the gaurdians of all ar info: Will a 1:7 twist shoot 55grn ammo without increased barrel wear or decreased accuracy when compared to a 1:9 twist???????????

Thanks
Link Posted: 9/7/2005 5:53:44 PM EDT
if it runs (which it should) then do it!

Link Posted: 9/7/2005 5:55:03 PM EDT
[Last Edit: 9/7/2005 5:55:30 PM EDT by mongo001]
Increased barrel wear -> myth. Even if there is, is it measurable????

1%????
0.1%????
0.01%????

Let's say it's 1% of a 20k livespan. That's 200rds.

Accuracy loss -> myth.

FWIW. My $0.02.
Link Posted: 9/7/2005 6:16:57 PM EDT
Wolf 55gr shoots pretty well......

I bet better ammo would too.

WIZZO
Link Posted: 9/7/2005 6:34:48 PM EDT
Don't think the barrel wear will be an issue with the 55 gr. for you, some believe the 1-7 twist wears faster. I have never seen this proven, but a 55gr bullet should be more accurate in a 1-9 twist in general but rifle barrels are individual and the only way to know for sure is to try it.

We shoot 52 and 53gr match bullets all the time out of 1-7 and 1-8 twist barrels with great accuracy in reduce course competition. But if you must limit yourself to a 55 or similar weight bullet, then the 1-9 would be a better choice and give you a better chance at greater accuracy. There is no definitive answer for your question other then 1-9 would be more optimal but not always more accurate.
Link Posted: 9/7/2005 7:13:52 PM EDT
Im gonna go with decreased accuracy DEPENDING on grade of the bullet. If you have bullet that is some what out of round, even just a little bit. The faster turning 1/7 is going to bring that defect out, more so than a 1/9. That being said, many shooters shoot wolf through 1/7, and have no problems at all.
Link Posted: 9/7/2005 8:09:25 PM EDT
Here's what I think: The 1 in 7 twist will wear out slightly faster than the 1 in 9 twist and it doesn't matter what grain bullets you shoot. Is the greater wear something to be concerned about? No, I don't think so.

The 1 in 7 twist will also be slightly less accurate than the 1 in 9 with 55grn and lighter bullets because the bullet will be over stabilized. Unless you're trying to shoot half inch groups at 200 yards though it won't matter. Don't worry about it.

If most of your shooting is going to be with 68grn (or 69grn) or less then get the 1 in 9 twist barrel. If most of your shooting is going to be with 62 grn or more bullets then get the 1 in 7 twist barrel.
Link Posted: 9/7/2005 8:17:52 PM EDT
Kris

I am not sure if over stabilization is really in issue, that only effect projectiles on the downward branch of the trajectory. And in really, since it would be a uniform effect on all the projectiles, I am not sure if you could see a discernible difference. Now granted some tubes may not shoot a certain load well, but I don't think you can make an across the board assessment such as 1-7 will always be less accurate.
Link Posted: 9/7/2005 8:55:51 PM EDT
Hi STLRN,

I did not intend to say that 1 in 7 twist bbls would always be less accurate. They will certainly (generally?) be more accurate than 1 in 9 twist bbls with 75grn and higher bullets.

I think I understand what you're saying about over stabilization and its affect on accuracy. Makes sense. I have a 14.5 inch 1 in 9 twist bbl and a 16 inch 1 in 7 twist bbl. I may run some tests next time I'm at the range and report back. It'll be a few weeks though....
Link Posted: 9/8/2005 3:06:03 AM EDT
Anybody tried the 69grs Sierra Matchking in a barrel with 1:9 twist? Is it too heavy?
Link Posted: 9/8/2005 3:13:51 AM EDT

Originally Posted By Storegnu:
Anybody tried the 69grs Sierra Matchking in a barrel with 1:9 twist? Is it too heavy?



Thats a fine combo. As heavy as you can go though.

I have never had an issue shooting 55 gr bullets from a 1/7 all the way (on paper) to 300 yards. I was shooting 3-4 MOA at 300, but that was on a silhouette target, with an aimpoint, using the magazine as a monopod. I don't think that was too bad for a CL barrel and uber cheap practice ammo. And a 7# trigger.
Link Posted: 9/8/2005 3:55:42 AM EDT
I had this 1/7 do it all thought for a while, I got multiple upper instead, the most I use is the 1/9 which is for 55 and 62 gr. wolf ammo. Now Im' saving for multiple barelled upper.
Link Posted: 9/8/2005 4:05:49 AM EDT
[Last Edit: 9/8/2005 4:06:26 AM EDT by Hokie]
A 1:7 barrel will handle a 55 grain bullet like a 1:9 barrel will handle a 77 grain bullet - just fine.

You're accuracy might suffer a tad, but you'll still hit a 12" target at 200 yards. When shooting a 55 grain bullet out of a 1:7 barrel, you may notice the bullet sort of overspins itself due to the tight spiraling - most likely at extended ranges. The opposite is true shooting a 77 grain bullet from a 1:9 barrel. Accuracy still suffers.

If I had to sum it up if you're using your AR as solely a defense gun against would be ..... terrorists. Then I'd get a 1:7 barrel and buy thousands upon thousands of rounds of 77 grain ammo.

All my stuff is 1:9, cause I shoot primarily 62 grain ammo. Plus, it seems around here, 55 grain is all the local dealers have on the shelf.

Link Posted: 9/8/2005 4:16:16 AM EDT

Originally Posted By mongo001:
Increased barrel wear -> myth. Even if there is, is it measurable????

1%????
0.1%????
0.01%????

Let's say it's 1% of a 20k livespan. That's 200rds.

Accuracy loss -> myth.

FWIW. My $0.02.



+1 Mongo has spoken
Link Posted: 9/8/2005 5:52:01 AM EDT

Originally Posted By mongo001:
Increased barrel wear -> myth. Even if there is, is it measurable????

1%????
0.1%????
0.01%????

Let's say it's 1% of a 20k livespan. That's 200rds.

Accuracy loss -> myth.

FWIW. My $0.02.



+1000
Link Posted: 9/8/2005 6:01:21 AM EDT
Rifle: LMT upper 14.5" 1/7 twist, KAC RAS II, Aimpoint M2, Bushmaster lower w/RRA 2-stage trigger

Range = 50 yards

Win Q3131A 55grn. M193



Win 45grn. JHP (Walmart Value box)


Note: 4 MOA red-dot completely covered this small dot, (tested mainly to see if they'll shoot without slinging themselves apart)


Not only will M193 shoot but even the lighter 45grn JHP shoots quite well, so no worries.

Mike

ps - btw, I don't buy into any of this increased wear BS
Link Posted: 9/8/2005 6:27:26 AM EDT

Originally Posted By mr_wilson:
Rifle: LMT upper 14.5" 1/7 twist, KAC RAS II, Aimpoint M2, Bushmaster lower w/RRA 2-stage trigger

Range = 50 yards

Win Q3131A 55grn. M193
photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=12785


Win 45grn. JHP (Walmart Value box)
photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=13582

Note: 4 MOA red-dot completely covered this small dot, (tested mainly to see if they'll shoot without slinging themselves apart)


Not only will M193 shoot but even the lighter 45grn JHP shoots quite well, so no worries.

Mike

ps - btw, I don't buy into any of this increased wear BS



50 yd. range at American Shooting Center??

Link Posted: 9/8/2005 6:33:28 AM EDT

Originally Posted By Combat_Jack:

Originally Posted By Storegnu:
Anybody tried the 69grs Sierra Matchking in a barrel with 1:9 twist? Is it too heavy?



Thats a fine combo. As heavy as you can go though.



Well, that is very barrel dependant. I regularly shoot 75gr TAP through my 11.5" 1/9 twist
Bushy barrel and the accuracy is pretty much the same as with 55gr, maybe a tiny bit better.

Link Posted: 9/8/2005 6:36:36 AM EDT
i have shot 55gr xm and q3131a out of my 1x7 recon bbl. with no problems and great accuracy.
Link Posted: 9/8/2005 6:47:17 AM EDT
[Last Edit: 9/8/2005 2:22:39 PM EDT by arowneragain]
Yesterday evening - while in a hurry with only a minute or two to shoot - I shot a 8" group at 275 yards with 55 grain winchester 'white box' ammo from a 14.5" chrome-lined 1-7" twist LMT upper.

The optic was an Eotech - no magnification. No special effort was made at precision - red dot on the center of big cardboard box, pull trigger, repeat.

One of these days I'm gonna get bored and put a real scope on this upper and shoot it some and see what it will actually do when I can see the target. I wouldn't be surprised to see groups shrink by 50%.


edit:

that was 5 shots, not 3.
Link Posted: 9/8/2005 2:02:07 PM EDT
[Last Edit: 9/8/2005 2:02:35 PM EDT by M4Madness]
I've never shot anything but Lake City XM193 (55-grain) out of my 1/7 Colt barrel.
Link Posted: 9/8/2005 2:21:13 PM EDT
CMMG 14.5" M4 bbl. 1:7 twist using 55gr. UMC, SA, S&B, Black Hill, Lake City. All shoots great. Better groups with Black Hills and LC (100yds. 14"x10" steel plate).

I prefer shooting 62gr. though.
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