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Posted: 3/29/2009 6:04:03 AM EDT
I have searched, and don't see exactly what I am looking for.
Any reason light weight bullets - 55gr - will not adequeately stabilize in a 1:9 and 1:7 twist barrel?

Also, What about 1:9 twist and heavier bullets - 62, 69, and 75 grain bullets.

Thanks.
Link Posted: 3/29/2009 6:12:44 AM EDT
Originally Posted By CAP:
I have searched, and don't see exactly what I am looking for.
Any reason light weight bullets - 55gr - will not adequeately stabilize in a 1:9 and 1:7 twist barrel?

Also, What about 1:9 twist and heavier bullets - 62, 69, and 75 grain bullets.

Thanks.


55-62 gr will stabilize in a 1:9 twist barrel, a 1:7 will stabilize 55gr-75gr.
Link Posted: 3/29/2009 6:15:12 AM EDT
my box of hornady 68 gr match bullets says they are good for 7-10 twist
Link Posted: 3/29/2009 6:17:00 AM EDT
[Last Edit: 3/29/2009 6:17:30 AM EDT by MMcfpd]
All of my barrels are either 1:9 or 1:7. The heaviest I shoot are 68 grain and that's fine with both twists as is 55 grain.
Link Posted: 3/29/2009 6:20:39 AM EDT
Tons of posts concerning this. Most barrels will shoot 55-69 gr. quite well. 1/7 is better for things 70 gr. and above.
Link Posted: 3/29/2009 6:46:25 AM EDT
Biggest factor to determine the proper twist to stabilize a bullet is the length of the bullet. BUT, since the bullets has to be the same diameter and most are the same basic profile, the length will vary pretty darn close to directly with the length. SO, the gouge you hear is still correct.

I believe the gouge is close to this:
1/9 twist, 55-62gr
1/7 twist, 62-85gr

The most accurate would be to put the exact amount of spin needed on the bullet, if you can't have that, then more spin is usually better than less spin.

I think factors like how balanced or how consistent the bullet is made will affect how well it stabilizes with a certain twist. i.e. those that say that Hornady bullets stabilize in their barrel that supposedly has to little twist to stabilize it. Speed of the bullet as well, so some rounds may have a different muzzle velocity and stabilize better with a certain twist than others.

I think, don't really know, the only time to much spin hurts a bullet is far out, near the end of its ballistic arc (long range). Might be why you see folks talk about their 1/7 barrel shooting 55gr just great, because at most plinking ranges, even mid range target shooting, that extra spin isn't hurting.

You'll get a dozen different opinions, many will tell you their 1/7 barrels shoot everything perfect, others will tell you they get the most accuracy with the barrel that has a twist closest to the gouge for the weight of bullet they are shooting, other will say the same, but they have found a few exceptions where they can shoot one brand/type of round that is lighter/heavier than the gouge.

Like anything with a design, the parameters you select are often a compromise to best cover the conditions you'll use the design in.

Figure out what you want to shoot and then select the best twist in a barrel to shoot that weight ammo. If you want to shoot everything, get the 1/7 twist, you'll just over spin the lighter rounds, some say they are still perfectly accurate like that. Many people are very happy with their 1/9 barrels because they only shoot the cheaper 55gr and sometimes the 62gr stuff.

The gouge about the Military selecting the 1/7 twist barrel is that they have to shoot tracers which are much longer bullets for equal weight to non-tracers.
Link Posted: 3/29/2009 8:03:00 AM EDT
Originally Posted By USMC-Helo:
Biggest factor to determine the proper twist to stabilize a bullet is the length of the bullet. BUT, since the bullets has to be the same diameter and most are the same basic profile, the length will vary pretty darn close to directly with the length. SO, the gouge you hear is still correct.

I believe the gouge is close to this:
1/9 twist, 55-62gr
1/7 twist, 62-85gr

The most accurate would be to put the exact amount of spin needed on the bullet, if you can't have that, then more spin is usually better than less spin.

I think factors like how balanced or how consistent the bullet is made will affect how well it stabilizes with a certain twist. i.e. those that say that Hornady bullets stabilize in their barrel that supposedly has to little twist to stabilize it. Speed of the bullet as well, so some rounds may have a different muzzle velocity and stabilize better with a certain twist than others.

I think, don't really know, the only time to much spin hurts a bullet is far out, near the end of its ballistic arc (long range). Might be why you see folks talk about their 1/7 barrel shooting 55gr just great, because at most plinking ranges, even mid range target shooting, that extra spin isn't hurting.

You'll get a dozen different opinions, many will tell you their 1/7 barrels shoot everything perfect, others will tell you they get the most accuracy with the barrel that has a twist closest to the gouge for the weight of bullet they are shooting, other will say the same, but they have found a few exceptions where they can shoot one brand/type of round that is lighter/heavier than the gouge.

Like anything with a design, the parameters you select are often a compromise to best cover the conditions you'll use the design in.

Figure out what you want to shoot and then select the best twist in a barrel to shoot that weight ammo. If you want to shoot everything, get the 1/7 twist, you'll just over spin the lighter rounds, some say they are still perfectly accurate like that. Many people are very happy with their 1/9 barrels because they only shoot the cheaper 55gr and sometimes the 62gr stuff.

The gouge about the Military selecting the 1/7 twist barrel is that they have to shoot tracers which are much longer bullets for equal weight to non-tracers.


'gouge' You keep using this word. I do not think it means what you think it means.

I've shot some 50gr and a whole lot of 55gr from my 1/7 barrels. I get the best accuracy with 75gr OTM with groups around 1.5MOA. The 50gr stuff gets me 2 to 2.25MOA.

BSW

Link Posted: 3/29/2009 9:03:36 AM EDT
Allow me to restate: The purpose/reason for the Military selecting the 1/7 twist barrel is that they have to shoot tracers, which are 20% longer than non-tracer bullets of near equal weight, in all climates from the Arctic Box to the Sand Box.
Link Posted: 3/29/2009 10:11:45 AM EDT
Gouge, at least the way we used in the Marines, was a helpful tip, condensed information or insight. Since it was word of mouth, or condensed down rules of thumb, you always had to be careful that the "gouge" may NOT be applicable.

What do you think "gouge" means?
Link Posted: 3/29/2009 10:14:46 AM EDT
Originally Posted By USMC-Helo:
Gouge, at least the way we used in the Marines, was a helpful tip, condensed information or insight. Since it was word of mouth, or condensed down rules of thumb, you always had to be careful that the "gouge" may NOT be applicable.

What do you think "gouge" means?


Ahhhh! You're using the most obscure, least common, slang meaning.

http://en.wikipedia.org/wiki/Gouge

BSW
Link Posted: 3/29/2009 10:18:57 AM EDT
1/7 is gtg 55gr and up
Link Posted: 3/29/2009 10:37:03 AM EDT
[Last Edit: 3/29/2009 10:38:14 AM EDT by USMC-Helo]
From your source:
U.S. Navy Slang

In U.S. Navy jargon, gouge is the essential piece of information; the heart of the matter; or outstanding test-preparation material (such as an old test copy). A person who is tired of hearing all the extraneous information surrounding a problem might exclaim "Just give me the gouge!"

Originated at the U.S. Naval Academy and introduced from there into the wider navy, where it sees less frequent usage.

That's the way we used it at Annapolis, I saw it more used in the Marines than Navy. That condensing of just the needed information, usually became rules of thumbs, either noted down or passed along as word of mouth. It became more than just the info to help pass a test, it was also notes and tips on procedures, specs, etc.

Really don't see how its much different than how I used it. Considering how we can spend pages debating rifle twist, with lots of conflicting references and a hundred people chiming in the total opposite extremes; and considered I've probably fired 1/10th as much as some of the experts on this board, as well never any of the bigger grain ammo, I left it at the info I've seen most people agree on, and called it the gouge. Its been passed to me as gouge. I may be wrong on the upper limit of the 1/7 twist for the heaviest grain bullet you can fire, since I never owned a 1/7 barrel, just fired them active duty.
Link Posted: 3/29/2009 10:48:16 AM EDT
[Last Edit: 3/29/2009 10:50:59 AM EDT by Molon]
Originally posed by CAP:

have searched, and don't see exactly what I am looking for.
Any reason light weight bullets - 55gr - will not adequeately stabilize in a 1:9 and 1:7 twist barrel?


Contrary to some of the nonsense that you may have read on the Internet, quality 55 grain bullets can shoot superbly from fast twist barrels. The 10-shot group pictured below was fired from an AR-15 with a Krieger barrel with a 1:7.7” twist barrel using 55 grain BlitzKings.






“Overspinning” a quality 55 grain bullet from a fast twist barrel does not become an issue unless you have a gyroscopic stability factor greater than 5.0 (which would require something along the lines of a 1:6” twist barrel launching the bullet at over 3500 fps) or unless firing at an angle greater than 85 degrees.
Link Posted: 3/29/2009 11:03:45 AM EDT
I have read that with a 1/7 twist barrel that shooting lighter 40-50 grain bullets will yeild less accuracy becasue they are over spun. This causes them to yaw up ward as they are first released from the barrel but after lets say 100-150 yards the nose comes back down and the accuracy returns to a little bit closer to what 62gr rounds would achive. I know this wasnt a great description. I know there ahve been other posts on here about it and there have been magazine articles about it too.
Link Posted: 3/29/2009 11:13:02 AM EDT
Link Posted: 3/29/2009 11:14:00 AM EDT
[Last Edit: 3/29/2009 11:15:40 AM EDT by mrraley]
Link Posted: 3/29/2009 12:40:08 PM EDT
[Last Edit: 3/29/2009 12:44:53 PM EDT by CAP]
I should have noted, that I am talking about commercially mass produced ammunition here - M193, M855, LC, Federal, PMC and the like, in both .223 and 5.56. I know there are vast differences in those I noted here.
Thanks to all for the additional input.

ETA: the reason I was asking it that I have al older 1:12 twist AR, much newer 1:7 twist Colt barrelled AR, and am contemplating getting in on the Stag group buy, which would be a 1:9 twist barrel.
Trying to decide which weight to focus on purchasing for them. I know the 1:12 will nto stabilize the heaver bullets.

Link Posted: 3/29/2009 12:55:51 PM EDT
Originally Posted By Molon:
Originally posed by CAP:

have searched, and don't see exactly what I am looking for.
Any reason light weight bullets - 55gr - will not adequeately stabilize in a 1:9 and 1:7 twist barrel?


Contrary to some of the nonsense that you may have read on the Internet, quality 55 grain bullets can shoot superbly from fast twist barrels. The 10-shot group pictured below was fired from an AR-15 with a Krieger barrel with a 1:7.7” twist barrel using 55 grain BlitzKings.



http://www.box.net/shared/static/gos6vq3szi.jpg


“Overspinning” a quality 55 grain bullet from a fast twist barrel does not become an issue unless you have a gyroscopic stability factor greater than 5.0 (which would require something along the lines of a 1:6” twist barrel launching the bullet at over 3500 fps) or unless firing at an angle greater than 85 degrees.



/thread



Link Posted: 3/29/2009 2:28:42 PM EDT
In spite of all the numbers, I remember reading that the 1 in 12 twists we had on our early M16 barrels was to "de-stabilize" the bullet, causing the famous deadly "tumble'. O therwise , you're just punching 1/4" holes in things. The idea of a military rifle is to kill humans at medium range. 1 in 12 was perfect for this. The AR platform has expanded and diversified, as has the choice of rifling. Killing "varmints" was never considered in the design.
Link Posted: 3/29/2009 2:38:22 PM EDT
[Last Edit: 3/29/2009 2:40:09 PM EDT by Molon]
Originally Posted By anjong-ni:
In spite of all the numbers, I remember reading that the 1 in 12 twists we had on our early M16 barrels was to "de-stabilize" the bullet, causing the famous deadly "tumble'.



Please tell me this is your lame attempt at humor.

Link Posted: 3/29/2009 3:20:51 PM EDT
Sorry Molon, no humor. I live in a lousy neighborhood. My home and family are defended by an AR15 with 1 in 12 twist. " Varmints" probably won't try to break in. To the OP: Build your AR to take on YOUR target. My last take on the subject. Phil US Army 1970 - 1974. In the rice paddies '72 - '73.
Link Posted: 3/29/2009 3:24:15 PM EDT
[Last Edit: 3/29/2009 3:25:13 PM EDT by Molon]
Originally Posted By anjong-ni:
Sorry Molon, no humor. I live in a lousy neighborhood. My home and family are defended by an AR15 with 1 in 12 twist. " Varmints" probably won't try to break in. To the OP: Build your AR to take on YOUR target. My last take on the subject. Phil US Army 1970 - 1974. In the rice paddies '72 - '73.


Then you as much as anyone should be arming yourself with facts pertaining to terminal ballistics. Your statement about the reason the 1:12" twist barrel was used on early AR-15s is pure urban legend.

Link Posted: 3/29/2009 3:34:45 PM EDT
Originally Posted By Molon:
Originally Posted By anjong-ni:
Sorry Molon, no humor. I live in a lousy neighborhood. My home and family are defended by an AR15 with 1 in 12 twist. " Varmints" probably won't try to break in. To the OP: Build your AR to take on YOUR target. My last take on the subject. Phil US Army 1970 - 1974. In the rice paddies '72 - '73.


Then you as much as anyone should be arming yourself with facts pertaining to terminal ballistics. Your statement about the reason the 1:12" twist barrel was used on early AR-15s is pure urban legend.



Just like the AK was designed to shoot the 5.56 in an emergency. That one goes throught the military too.

I respect anyone who served a great deal. But that does not make them ballisticians.
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