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Posted: 10/29/2003 4:41:33 PM EDT
As I look at new AR's it seems that only a few have a 1/7 twist. How heavy a load (bullet Weight)are useable in a 1/9 twist?? For people that have 1/7 twists, does the average shooter use the full spectrum of ammo to utilize the capacity of the 1/7 twist barrel??
Link Posted: 10/29/2003 4:44:19 PM EDT
[Last Edit: 10/29/2003 4:44:57 PM EDT by MaverickMkii]
Recommended maximum: 69gr (this is guaranteed) Absolute maximum: 75/77gr (most of the time it doesn't work. but for some people it works especially if they are using this for non-competition-type shooting)
Link Posted: 10/29/2003 5:04:36 PM EDT
Originally Posted By MaverickMkii: Recommended maximum: 69gr (this is guaranteed) Absolute maximum: 75/77gr (most of the time it doesn't work. but for some people it works especially if they are using this for non-competition-type shooting)
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I'd agree with this post except for one comment: [b][i]most of the time it doesn't work[/b][/i] In my experience most of the time IT DOES WORK. Heck, the Black Hills 75gr boxes are even marked "[i]For use in 1:9 twist or faster[/i]".
Link Posted: 10/30/2003 10:39:22 AM EDT
oh you are right I have seen that. I always thought 1/9 was 69
Link Posted: 10/30/2003 11:06:59 AM EDT
Originally Posted By Forest:
Originally Posted By MaverickMkii: Recommended maximum: 69gr (this is guaranteed) Absolute maximum: 75/77gr (most of the time it doesn't work. but for some people it works especially if they are using this for non-competition-type shooting)
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I'd agree with this post except for one comment: [b][i]most of the time it doesn't work[/b][/i] In my experience most of the time IT DOES WORK. Heck, the Black Hills 75gr boxes are even marked "[i]For use in 1:9 twist or faster[/i]".
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Ok, so if a 1:9 can stabilize a 75gr, why do so many people suggest buying the 1:7? Are THAT many people shooting heavier than a 75gr bullet??? I've always heard the 1:9 was the most versatile of the barrels. Not to fast for the light rounds and fast enough for the 75s.
Link Posted: 10/30/2003 12:01:35 PM EDT
Many people want 1/7 barrels because that's the military standard de jour. It's my understanding that the tracer round currently in use may not stabilize well in a 1/9 due to its length, so 1/7 is the military standard. 75gr will work out of a 1/9, and I've shot 77gr SMK's with good results. Once you get up into the 75-77gr range, you just have to try some and see how the particular load works in your particular rifle. It's at the upper end of the limit, for sure.
Link Posted: 10/30/2003 12:19:16 PM EDT
1/9 is often not accurate with 75 and 77 grain ammo. There have been several members who could not tget their 1/9 twist to shoot 75 or 77 grain ammo. Its not that 1/9 wont work but 1/7 ALWAYS works.
Link Posted: 10/30/2003 12:34:54 PM EDT
Originally Posted By DaPhotoGuy: Ok, so if a 1:9 can stabilize a 75gr, why do so many people suggest buying the 1:7?
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Several reasons: 1) You KNOW it will work (none of that will it or won't it B.S). 2) Better accuracy. 1:9 Will stabilize the round but you won't get the same level of accuracy. I'm happy if it will keep groups in 4" from the prone position - my 1:9 barrels will do that easily. But groups won't be as tight as 55gr or 68gr. 3) 1:7 will allow you to move to even heavier bullets should the need evovle (say for new bullet designs).
Link Posted: 10/30/2003 1:25:27 PM EDT
Originally Posted By DevL: 1/9 is often not accurate with 75 and 77 grain ammo. There have been several members who could not tget their 1/9 twist to shoot 75 or 77 grain ammo. Its not that 1/9 wont work but 1/7 ALWAYS works.
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Then the only DOWNSIDE to 1:7 is that it over spins the light bullets, right?
Link Posted: 10/30/2003 1:42:39 PM EDT
Originally Posted By Forest: 2) Better accuracy. 1:9 Will stabilize the round but you won't get the same level of accuracy. I'm happy if it will keep groups in 4" from the prone position - my 1:9 barrels will do that easily. But groups won't be as tight as 55gr or 68gr.
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Forest, You are quite right when you say 75/77gr works in 1/9. I hope it does in mine too because I don't want to swap my barrel just because I wanted to use heavier loads. If your standard of "working" is 4 MoA, I agree with you since thats all that is needed for defensive type shooting. But for some folks if they don't get 1 MoA they will not use the ammo. My notion of "not working" was that, which would be useless for competition shooters. I guess I should have worded better.
Link Posted: 10/30/2003 4:01:56 PM EDT
Originally Posted By DaPhotoGuy:
Originally Posted By DevL: 1/9 is often not accurate with 75 and 77 grain ammo. There have been several members who could not tget their 1/9 twist to shoot 75 or 77 grain ammo. Its not that 1/9 wont work but 1/7 ALWAYS works.
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Then the only DOWNSIDE to 1:7 is that it over spins the light bullets, right?
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Yes and this results in a VERY slight loss of accuracy with ammo down to 55 grains. You would not be able to shoot certain ammo under that weight as it would break apart in flight on occasion.
Link Posted: 10/30/2003 4:12:43 PM EDT
I have some 45 grain SP loads I cannot shoot in my 1/9" bbl. They are great in a 1/12", though.
Link Posted: 10/30/2003 6:09:32 PM EDT
I wish the major manufacturers offered a production 1:12" bbl as an option. The combination of this twist rate plus M193 is what yielded excellent results in the very early part of Vietnam.
Link Posted: 10/30/2003 7:09:44 PM EDT
Originally Posted By chuckhammer: The combination of this twist rate plus M193 is what yielded excellent results in the very early part of Vietnam.
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Twist rate has nothing to do with the effectiveness of the ammo. As long as the twist rate stabilizes the ammo you are fine. Please read the articles by Dr. Fackler posted at the top of this forum. It covers this in the article [u]Wounding Patterns of Military Rifle Bullets[/u]
Link Posted: 10/30/2003 7:21:56 PM EDT
[Last Edit: 10/30/2003 8:13:51 PM EDT by chuckhammer]
Originally Posted By Forest:
Originally Posted By chuckhammer: The combination of this twist rate plus M193 is what yielded excellent results in the very early part of Vietnam.
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Twist rate has nothing to do with the effectiveness of the ammo. As long as the twist rate stabilizes the ammo you are fine. Please read the articles by Dr. Fackler posted at the top of this forum. It covers this in the article [u]Wounding Patterns of Military Rifle Bullets[/u]
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I wiil be sure to read the article but it's safe to say the tighter you twist a projectile the more stabilized it becomes. This is a bad thing when you want the projectile to yaw as quickly as possible in the target medium. Also, the tighter you twist a projectile the more velocity it will lose in overcoming friction. Pretty simple: the projectile starts off with a given amount of kinetic energy. It will use some of this to begin spinning at the rifling twist rate. Any twist rate greater than the minium required to stabilize the projectile will result in an unnecessarily decreased muzzle velocity. Therefore, any twist rate greater than the minimum required to stabilze the projectile is a waste of muzzle velocity.
Link Posted: 10/30/2003 7:59:53 PM EDT
Originally Posted By chuckhammer:
Originally Posted By Forest:
Originally Posted By chuckhammer: The combination of this twist rate plus M193 is what yielded excellent results in the very early part of Vietnam.
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Twist rate has nothing to do with the effectiveness of the ammo. As long as the twist rate stabilizes the ammo you are fine. Please read the articles by Dr. Fackler posted at the top of this forum. It covers this in the article [u]Wounding Patterns of Military Rifle Bullets[/u]
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I wiil be sure to read the article but it's safe to say the tighter you twist a projectile the more stabilized it becomes. This is a bad thing when you want the projectile to yaw as quickly as possible in the target medium. Also, the tighter you twist a projectile the more velocity it will lose in overcoming friction. Pretty simple: the projectile starts off with a given amount of kinetic energy. It will use some of this to begin spinning at the rifling twist rate. Any twist rate greater than the minium required to stabilize the projectile will result in an unnecessarily decreased muzzle velocity. Therefore, any twist rate greater than the minimum required to stabilze the projectile is a waste of muzz;e velocity.
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According to everything I've read you are correct!
Link Posted: 10/30/2003 8:21:46 PM EDT
Originally Posted By chuckhammer:
Originally Posted By Forest: [b]Twist rate has nothing to do with the effectiveness of the ammo. As long as the twist rate stabilizes the ammo you are fine. Please read the articles by Dr. Fackler posted at the top of this forum. It covers this in the article [u]Wounding Patterns of Military Rifle Bullets[/u]
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I wiil be sure to read the article but it's safe to say the tighter you twist a projectile the more stabilized it becomes. This is a bad thing when you want the projectile to yaw as quickly as possible in the target medium.[/b]
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I read the article and it seems experimantation has shown the greater amount of stability given to a projectile via increased twist rate is insignificant when compared to the drag forces encountered once inside the target medium. In other words, you are correct.
[b]Also, the tighter you twist a projectile the more velocity it will lose in overcoming friction. Pretty simple: the projectile starts off with a given amount of kinetic energy. It will use some of this to begin spinning at the rifling twist rate. Any twist rate greater than the minium required to stabilize the projectile will result in an unnecessarily decreased muzzle velocity. Therefore, any twist rate greater than the minimum required to stabilze the projectile is a waste of muzzle velocity.[/b]
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This statement is still true. The effects of "overspinning" the projectile would be slightly decreased muzzle velocity, and ultimately, mid-flight fragmentation, assuming extreme "overspinning" had occured.
Link Posted: 10/31/2003 12:57:25 AM EDT
On the Bushmaste site they say that their 1-9 twist barrels with work with a 74 grain bullet. They also say up to a 80 grain but the accuracy will suffer. A 1-7 twist will do a better job at stabilizing a 75 grain bullet and higher, probably even a 69 grain. The 1-7 will work with a 55 grain but I think that the accuracy will probably suffer just like the heavier bullets will in a 1-9. Their are allot of members who have posted that their 1-9 twist rifles will not work properly with the 75 grain bullets, some say they work just fine. That tells me that the 75-77 grain bullets are pressing it in a 1-9 twist barrel. The only way to know for sure is to give it a try and compare it to the lighter rounds in your rifle. I have also heard that the 20" 1-9 twist barrels work better then the 16" 1-9 twist barrels with the heavier bullets.
Link Posted: 10/31/2003 4:59:27 AM EDT
Originally Posted By chuckhammer: I wiil be sure to read the article but it's safe to say the tighter you twist a projectile the more stabilized it becomes. This is a bad thing when you want the projectile to yaw as quickly as possible in the target medium.
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The problem with that idea is the target medium is very dense it really doesn't matter. Realistically you can't spin the projectile fast enough to stabilize in flesh.
Therefore, any twist rate greater than the minimum required to stabilze the projectile is a waste of muzzle velocity.
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Funny I don't see a significant difference measureing the MV from a 1:12, 1:9 or 1:7 20" shooting M193. Again go and read what the Docotor wrote. His work is based on experience and experimentation. Dr Fackler indicates twist rate has no effect on the wounding.
Link Posted: 10/31/2003 5:50:21 AM EDT
Originally Posted By Forest:
Originally Posted By chuckhammer: I wiil be sure to read the article but it's safe to say the tighter you twist a projectile the more stabilized it becomes. This is a bad thing when you want the projectile to yaw as quickly as possible in the target medium.
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The problem with that idea is the target medium is very dense it really doesn't matter. Realistically you can't spin the projectile fast enough to stabilize in flesh.
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Yes, and that's what I said in my second post after reading Fackler's article. Experimentation shows this to be correct.
Therefore, any twist rate greater than the minimum required to stabilze the projectile is a waste of muzzle velocity.
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Funny I don't see a significant difference measureing the MV from a 1:12, 1:9 or 1:7 20" shooting M193.
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Nothing funny about it. I don't own a chrono; I was merely using the law of conservation of energy to figure in a slight loss in muzzle velocity. I guess it's not a significant loss, probably within the error of the powder charge and instrumentation (5-15 fps).
Link Posted: 10/31/2003 8:27:42 AM EDT
Less friction does NOT mean more velocity. Moly coated bullets for example will reduce friction and pressure and lower velocity and you have to up the powder charge to get the velocity back. Think of a spit ball. THe ones really crammed in there have more pressure behind them to escape and fly faster. [;)]
Link Posted: 10/31/2003 12:06:25 PM EDT
Originally Posted By DevL: Less friction does NOT mean more velocity. Moly coated bullets for example will reduce friction and pressure and lower velocity and you have to up the powder charge to get the velocity back.
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I see what you're saying but I think that's a different phenomenon at work. Similar to your spitball analogy, the moly bullets slip out of the case neck too quickly before the pressure has a chance to build sufficiently. Once the bullet starts making its way down the bore, however, any extra friction it encounters will reduce velocity, even as the pressure stays high behind it. Think about trying to shoot a .338 bullet in a .270 bore (humor me here). Both the friction force and pressure would be through the roof but the velocity sure wouldn't be very high.
Link Posted: 10/31/2003 1:41:03 PM EDT
I was told this. "The more twists in a barrel the more friction the bullet encounters and can destabilize and deter velocity. Although if you do not have enough twists the bullet will not stabilize and also could loose velocity. Its sa delicate balancing act with your ammo".
Link Posted: 10/31/2003 1:51:00 PM EDT
I guess this would be a good time to ask MY question: I'm planning to to on my first hunting trip with a friend later this season. Probably it'll be in search of deer. I'll be using my AR as it's the only centerfire rifle I have, and also it has the virtue of being extremely accurate. What would you recommend as the best bullet for a 1 in 9 twist barrel for deer? Barnes X? What? CJ
Link Posted: 11/4/2003 5:31:07 AM EDT
Read Feamsters comment on 1-7 twist barrels and bullet weights on page 57. He got the best accuracy with the 52 gr. sierra matchkings, and won the official screamer patch for shooting less than 1/4" at 200 meters.[shock]
Link Posted: 11/4/2003 6:06:22 AM EDT
Originally Posted By cmjohnson: I guess this would be a good time to ask MY question: I'm planning to to on my first hunting trip with a friend later this season. Probably it'll be in search of deer. I'll be using my AR as it's the only centerfire rifle I have, and also it has the virtue of being extremely accurate. What would you recommend as the best bullet for a 1 in 9 twist barrel for deer? Barnes X? What? CJ
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You ought to ask in the hunting forum, but I've seen a lot of reference to the Winchester 64gr PowerPoint as being a good deer load.
Link Posted: 11/4/2003 6:17:47 AM EDT
In case anyone cares about the lighter end of the bullet weight spectrum my handloaded Nosler 40gr Ballisitc tips were extremely accurate in my old 1/9ROT 20" Bushy, but were marginal in my 1/7ROT 20" Colts. They didn't always break the paper cleanly when shot out of the Colts either. It looked as though they were either not flying correctly, or maybe deforming in flight. They weren't fully keyholing, but the holes were frequently oval shaped or jagged, rather than perfectly round. I was experimenting with different bullets at the time-the problem vanished when I switched back to 55gr Noslers.
Link Posted: 11/8/2003 6:47:19 PM EDT
Originally Posted By chuckhammer: I wish the major manufacturers offered a production 1:12" bbl as an option. The combination of this twist rate plus M193 is what yielded excellent results in the very early part of Vietnam.
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Yeah my Colt AR-15 SP1 is 1:12 although it is 22 years old. May be able to pickup one cheap? Not mine of course - Not for Sale.
Link Posted: 11/10/2003 3:30:54 PM EDT
Originally Posted By cmjohnson: I guess this would be a good time to ask MY question: I'm planning to to on my first hunting trip with a friend later this season. Probably it'll be in search of deer. I'll be using my AR as it's the only centerfire rifle I have, and also it has the virtue of being extremely accurate. What would you recommend as the best bullet for a 1 in 9 twist barrel for deer? Barnes X? What? CJ
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You do need to check out the hunting forum as I think there is a thread on this over there right now. Also be sure you check the regs for the state you are hunting in, the 223 isn't legal to use on deer in every state. You can usually find this information really quickly on the state's wildlife service website.
Link Posted: 11/12/2003 7:45:01 AM EDT
Originally Posted By CJan_NH: In case anyone cares about the lighter end of the bullet weight spectrum my handloaded Nosler 40gr Ballisitc tips were extremely accurate in my old 1/9ROT 20" Bushy, but were marginal in my 1/7ROT 20" Colts. They didn't always break the paper cleanly when shot out of the Colts either. It looked as though they were either not flying correctly, or maybe deforming in flight. They weren't fully keyholing, but the holes were frequently oval shaped or jagged, rather than perfectly round. I was experimenting with different bullets at the time-the problem vanished when I switched back to 55gr Noslers.
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With the kinds of RPMs on a 40 grain bullet, they would probably not deform in flight, but fully disintegrate. The bullets were overspun, so that they continued to fly "nose up." Hence the oblong, but not fully keyholed, shape of the hole. YMMV
Link Posted: 11/12/2003 8:21:05 AM EDT
From the Ammo Oracle, graph of the path of an overspun bullet. The nose stays up, which results in the out-of-round holes in the paper. [img]http://www.ammo-oracle.com/images/overstable.jpg[/img]
Link Posted: 11/12/2003 4:18:58 PM EDT
Very interesting discussion guys, thanks for the information. I have some of the TAP 40gr IIRC for house work since the potential of over penetration is less with this weight. Any comments?
Link Posted: 11/13/2003 6:26:45 PM EDT
Originally Posted By TNRonin: I have some of the TAP 40gr IIRC for house work since the potential of over penetration is less with this weight. Any comments?
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Other than they don't meet the 12" minimum, nope. What barrel length do you have? I could look up the penetration numbers for you.
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