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Posted: 8/27/2014 8:18:24 AM EDT
[#1]
Not directly, but it does depend on what you mean by “longer ranges”.
Heavier bullets have better performance characteristics at long range. Some barrels marked 1:9 will handle heavier bullets, but it is not something a person can count on. |
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Posted: 8/27/2014 8:18:50 AM EDT
[#2]
For longer range shots a heavier bullet is preferred due greater retained energy and less wind drift. Typically 1:9 does not properly stabilize bullets above 69gr, 70gr and above usually require 1:8 or 1:7.
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Posted: 8/27/2014 8:26:00 AM EDT
[#3]
How far would the effective range be with the 1:9 barrel with rounds at 69gr or under?
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Posted: 8/27/2014 8:31:07 AM EDT
[#4]
Quote HistoryQuoted:
How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? You also have to consider barrel length as well. The longer the barrel, the more stability and accuracy, thereby being more effective. |
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Posted: 8/27/2014 11:06:13 AM EDT
[#5]
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? There were some YouTube videos of a guy shooting 60gr V-maxes at 6 or 700 yards, I think he is using a 24" barrel, so they should be moving. They do fantastic out of a 1:9. I haven't done it, but I would imagine a heavier match bullet that stabilized would be good at least as far. How far do you want to shoot? |
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Posted: 8/27/2014 11:48:17 AM EDT
[#6]
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There were some YouTube videos of a guy shooting 60gr V-maxes at 6 or 700 yards, I think he is using a 24" barrel, so they should be moving. They do fantastic out of a 1:9. I haven't done it, but I would imagine a heavier match bullet that stabilized would be good at least as far. How far do you want to shoot? Quote HistoryQuoted:
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? There were some YouTube videos of a guy shooting 60gr V-maxes at 6 or 700 yards, I think he is using a 24" barrel, so they should be moving. They do fantastic out of a 1:9. I haven't done it, but I would imagine a heavier match bullet that stabilized would be good at least as far. How far do you want to shoot? Well the max range I have access to is 500 yards so I think Ill be fine then. Also of note though is my barrel will only be 16in |
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Posted: 8/27/2014 11:51:30 AM EDT
[#7]
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? 300+ yards All 1/9 barrels are generic production barrels. Most are chrome lined which doesn't help matters. That being said, my gun club's 200 yards slow fire (600 yard reduced target) range record has been held for over 20 years, 200-16x, and it was shot with a 24" 1/9 stainless steel SGW barrel and 69 grain SMK's. It won't tied or beaten any time soon. It was an early space gun manned by an extremely good shot. |
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Posted: 8/27/2014 12:17:49 PM EDT
[#8]
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? If you want a rifle that will shoot any bullet weight well, 1:7. If you want a rifle that may (all else equal) shoot a particular weight better, get a barrel with a twist rate that is optimum for that bullet weight. 1:7 = doesn't matter. 1:8 = probably doesn't matter but may not stabilize the heavier >70gr loads as well. 1:9 = 62gr or less. 1:12 = 55gr or less. As stated, the heavier match loads will generally due better at all ranges and especially "long" range. |
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Posted: 8/27/2014 12:35:29 PM EDT
[#9]
What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7?
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Posted: 8/27/2014 12:44:20 PM EDT
[#10]
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Well the max range I have access to is 500 yards so I think Ill be fine then. Also of note though is my barrel will only be 16in Quote HistoryQuoted:
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? There were some YouTube videos of a guy shooting 60gr V-maxes at 6 or 700 yards, I think he is using a 24" barrel, so they should be moving. They do fantastic out of a 1:9. I haven't done it, but I would imagine a heavier match bullet that stabilized would be good at least as far. How far do you want to shoot? Well the max range I have access to is 500 yards so I think Ill be fine then. Also of note though is my barrel will only be 16in Do yourself a favor and find an upper that has a 1/7 or 1/8 barrel. With those twists you will be ok with 55 to 77 grain ammo. |
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Posted: 8/27/2014 1:05:03 PM EDT
[#11]
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What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7? Yes. |
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Posted: 8/27/2014 1:51:50 PM EDT
[#12]
I went 1/8 for my LR rifle and I shoot 55-77gr through it no issues. Each twist rate has its advantages but most of the guys who do the marksmanship rifle shoots are running .223 Wylde chambers with 1/8 twist.
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Posted: 8/27/2014 2:26:31 PM EDT
[#13]
1/7 or 1/8. 1/9 is a crapshoot with heavy pills. For a pistol I would stick with 55-62gr projos where 1/9 would be fine.
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Posted: 8/27/2014 3:25:21 PM EDT
[#14]
I don't have any 1/9's so my opinion is a bit moot. But my opinion is that you probably won't have any problems reaching out to 500 with a 1/9 and the right load. But yeah, your choices of how heavy you go will be limited. The heavier bullets will buck the wind better too. So..... I remember reading an article about when they used the first AR's to compete in High Power competition. And they used 55 grain bullets with 1/12 twists. And they had to move their front posts for elevation. So a 1/9 and 68's and 69's are a sight better than that.
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Posted: 8/27/2014 6:59:53 PM EDT
[#15]
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300+ yards All 1/9 barrels are generic production barrels. Most are chrome lined which doesn't help matters. That being said, my gun club's 200 yards slow fire (600 yard reduced target) range record has been held for over 20 years, 200-16x, and it was shot with a 24" 1/9 stainless steel SGW barrel and 69 grain SMK's. It won't tied or beaten any time soon. It was an early space gun manned by an extremely good shot. Quote HistoryQuoted:
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? 300+ yards All 1/9 barrels are generic production barrels. Most are chrome lined which doesn't help matters. That being said, my gun club's 200 yards slow fire (600 yard reduced target) range record has been held for over 20 years, 200-16x, and it was shot with a 24" 1/9 stainless steel SGW barrel and 69 grain SMK's. It won't tied or beaten any time soon. It was an early space gun manned by an extremely good shot. Not sure what you mean by "generic production barrels." I built my current carbine with a CMMG 16" black nitride (they called it WASP), also called Melonite, treated 1:9" barrel. it is extremely accurate for a carbine profile and length barrel. MOA with good ammo. Yes, it is limited to 70 grain and less lead core ammo, but I don't shoot anything heavier. I do have a problem with the long for weight solid copper 70 grain Barnes TXS bullets. They will not stabilize in the 1:9, although lead core bullets do, so I limit the excellent Barnes TSX hunting bullets to the 62 grain load. It's as long or longer than most 70 grain bullets, but stabilizes just fine. I prefer 1:9 for most of the ammo that most of us shoot, between 55 grain and 62-64 grain lead core bullets. And, I occasionally shoot the hot little 35 grain Hornady Superformance NTX Varmint ammo. A 1:7 or even a 1:8 will typically not stabilize these little grenades, travellng at about 3,600 fps from a 16" barrel. If I were to want to shoot just about anything in a 5.56 carbine length barrel, excluding the 35 grain NTX, I would go with 1:8 and get a nitride barrel rather than chrome lined, if I wanted the combination of high accuracy, low maintenance, corrosion resistance and long barrel life. |
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Posted: 8/27/2014 7:32:12 PM EDT
[#16]
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How far would the effective range be with the 1:9 barrel with rounds at 69gr or under? Long enough that it's not going to matter in practical terms. There isn't going to be that much difference in practical terms of the transonic range of a 69gr bullet vs a 77gr bullet. If you really want to max out a 1:9 try the Berger 73gr OTM, Berger recommends that twist. You have a ton of shooting to do before you get to the point of shooting to transonic range and beyond, you'll have burned out your current barrel by then. |
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Posted: 8/27/2014 7:34:06 PM EDT
[#17]
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What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7? 1:8 is the fastest twist rate that is needed for even the longest bullets anyone is going to be shooting in an AR15. Are you really going to be shooting 75 or 77gr long range match bullets out of a 7" pistol barrel? |
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Posted: 8/27/2014 9:50:58 PM EDT
[#18]
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1:8 is the fastest twist rate that is needed for even the longest bullets anyone is going to be shooting in an AR15. Are you really going to be shooting 75 or 77gr long range match bullets out of a 7" pistol barrel? Quote HistoryQuoted:
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What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7? 1:8 is the fastest twist rate that is needed for even the longest bullets anyone is going to be shooting in an AR15. Are you really going to be shooting 75 or 77gr long range match bullets out of a 7" pistol barrel? If that's the only thing I can find I would. I thought for pistols that the heavier stuff was better for SD because the XM193 didn't reach the velocity necessary to work its magic out of anything shorter than 14 inches? Correct me if I'm wrong. |
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Posted: 8/27/2014 10:15:42 PM EDT
[#19]
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If that's the only thing I can find I would. I thought for pistols that the heavier stuff was better for SD because the XM193 didn't reach the velocity necessary to work its magic out of anything shorter than 14 inches? Correct me if I'm wrong. Quote HistoryQuoted:
Quoted:
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What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7? 1:8 is the fastest twist rate that is needed for even the longest bullets anyone is going to be shooting in an AR15. Are you really going to be shooting 75 or 77gr long range match bullets out of a 7" pistol barrel? If that's the only thing I can find I would. I thought for pistols that the heavier stuff was better for SD because the XM193 didn't reach the velocity necessary to work its magic out of anything shorter than 14 inches? Correct me if I'm wrong. What magic?? 
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Posted: 8/27/2014 11:34:33 PM EDT
[#20]
In NRA high power, a rifle sport that uses AR15's at ranges of 200 to 600 yards, the standard load is either a 75 grain or 77 grain bullet. For these you need 1/7 or 1/8 twist.
Another popular (but not as popular in that sport) bullet is the 69 grain bullet or 68 grain bullet, which will work in a 1/9. I would get a 1/7 or 1/8 because I like the heavy bullets, and it allows you to use them if you want. |
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Posted: 8/28/2014 12:38:23 AM EDT
[#21]
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What magic?? Quote HistoryQuoted:
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What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7? 1:8 is the fastest twist rate that is needed for even the longest bullets anyone is going to be shooting in an AR15. Are you really going to be shooting 75 or 77gr long range match bullets out of a 7" pistol barrel? If that's the only thing I can find I would. I thought for pistols that the heavier stuff was better for SD because the XM193 didn't reach the velocity necessary to work its magic out of anything shorter than 14 inches? Correct me if I'm wrong. What magic?? 55gr XM193 bullets tumble when they hit a soft target, because the rear of the bullet is heavier than the front. If the bullet is above a certain velocity when it hits the target, the thin-jacketed bullet used in the XM193 load cannot sustain the pressures created when the bullet turns sideways a couple of times, so the thin jacket breaks, and the soft lead will violently erupt and fragment, creating very effective ballistics. If the bullet is traveling below that velocity, the chances that the bullet will fragment go way down, and the ballistics aren't so impressive. A 14" - 15" barrel is needed to get the XM193 to reach that velocity. If the barrel is too short, like a 9" pistol barrel, you'd be better off using a heavier bullet. That's what I remember about that cartridge. If I'm wrong about any of that, feel free to correct me. The XM193 is my favorite cartridge for my carbine for various reasons, but I've been told that a pistol will be more effective with a heavy load. |
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Posted: 8/28/2014 1:11:24 AM EDT
[#22]
Why not just use an appropriate bullet for defense instead?
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Posted: 8/28/2014 2:53:45 PM EDT
[#23]
Here is Stag Arms take on twist rates and bullet weight
http://info.stagarms.com/blog/bid/371861/How-Barrel-Twist-Rate-Affects-Ammunition-Choice |
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Posted: 8/28/2014 5:56:17 PM EDT
[#24]
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Why not just use an appropriate bullet for defense instead? Why don't you tell me what an appropriate bullet would be? |
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Posted: 8/28/2014 6:07:10 PM EDT
[#25]
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Why don't you tell me what an appropriate bullet would be? Quote HistoryQuoted:
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Why not just use an appropriate bullet for defense instead? Why don't you tell me what an appropriate bullet would be? http://www.ar15.com/ammo/project/Self_Defense_Ammo_FAQ/#.223 BARRIER BLIND LOADS ARE PREFERRED: There has been a shift away from fragmenting ammunition and toward barrier-blind bonded loads.
Doctor Roberts' latest take on this: "For LE and other individuals not restricted by the Hague convention, because of their good terminal performance across a wide spectrum of potential engagement scenarios, the bonded barrier blind projectiles have moved ahead of the fragmenting OTM loads we previously recommended, as the best general purpose loads available." If using a short-barreled weapon: The same guidelines apply as for barrier penetration loads. SBRs usually have insufficient velocity to achieve fragmentation velocity.
As per Doctor Roberts: "Keep in mind, that with non-fragmenting bullet designs, heavier bullet weights are not necessarily better, especially at closer ranges and from shorter barrels. As long as penetration and upset remain adequate, it is possible to use lighter weight non-fragmenting bullets and still have outstanding terminal performance. With fragmenting designs, a heavier bullet is ideal, as it provides more potential fragments and still allows the central core to have enough mass for adequate penetration. In addition, heavier bullets may have an advantage at longer ranges due to better BC and less wind drift." All the barrier blind defense loads will work fine in a 1:9 twist. Even if you preferred a fragmenting load, if your rifle doesn't shoot the 75gr Hornady you can use the 68gr Hornady as an alternative. If you handload the 73gr Berger is an excellent choice. Lighter weights give you more velocity which would give you a better chance of fragmentation. From the barrel lengths you're talking about, something like a 52gr OTM type might even be better. |
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Posted: 8/28/2014 6:12:58 PM EDT
[#26]
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1/7 or 1/8. 1/9 is a crapshoot with heavy pills. For a pistol I would stick with 55-62gr projos where 1/9 would be fine. The thing you're not factoring in for the pistol is terminal ballistics. The majority of 55gr and 62gr bullets don't perform very well at the slower velocities of a pistol. You're better off with the heavier stuff 69-77gr (barring some specialty ammo like some of the JSP offerings) with a pistol more so than you are with a precision 18" gun, which can shoot 55-77gr accurately and effectively. |
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Posted: 8/28/2014 6:16:30 PM EDT
[#27]
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Why not just use an appropriate bullet for defense instead? While I'll agree that there are better things out there, there is nothing wrong with using a 77gr SMK in an HD role out of a short barrel. They do work and from what I've seen don't penetrate barriers as much as some of the JSP offerings. ETA: Penetration should be a concern for most people in an HD role. The last thing I want while shooting a rifle in my home is ammo designed to penetrate barriers. I'm not going to be shooting through cover at an intruder in the next room. If I can't see them it is time to retreat, ensure 911 has been called, and set my self up with a good vantage point (hopefully shooting into a "fatal funnel") with decent cover until LE can arrive. I know all ammo will penetrate to a certain extent but I don't need something that is designed to do it from the get go. |
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Posted: 8/28/2014 8:23:45 PM EDT
[#28]
1:7 is the answer
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Posted: 8/28/2014 8:50:46 PM EDT
[#29]
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Even if you preferred a fragmenting load, if your rifle doesn't shoot the 75gr Hornady you can use the 68gr Hornady as an alternative. If you handload the 73gr Berger is an excellent choice. Lighter weights give you more velocity which would give you a better chance of fragmentation. From the barrel lengths you're talking about, something like a 52gr OTM type might even be better. Thanks! |
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Posted: 8/29/2014 1:00:22 PM EDT
[#30]
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55gr XM193 bullets tumble when they hit a soft target, because the rear of the bullet is heavier than the front. If the bullet is above a certain velocity when it hits the target, the thin-jacketed bullet used in the XM193 load cannot sustain the pressures created when the bullet turns sideways a couple of times, so the thin jacket breaks, and the soft lead will violently erupt and fragment, creating very effective ballistics. If the bullet is traveling below that velocity, the chances that the bullet will fragment go way down, and the ballistics aren't so impressive. A 14" - 15" barrel is needed to get the XM193 to reach that velocity. If the barrel is too short, like a 9" pistol barrel, you'd be better off using a heavier bullet. That's what I remember about that cartridge. If I'm wrong about any of that, feel free to correct me. The XM193 is my favorite cartridge for my carbine for various reasons, but I've been told that a pistol will be more effective with a heavy load. Quote HistoryQuoted:
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What's the best twist rate for a 7" to 9" pistol barrel if I want to be able to shoot any weight? Still 1:7? 1:8 is the fastest twist rate that is needed for even the longest bullets anyone is going to be shooting in an AR15. Are you really going to be shooting 75 or 77gr long range match bullets out of a 7" pistol barrel? If that's the only thing I can find I would. I thought for pistols that the heavier stuff was better for SD because the XM193 didn't reach the velocity necessary to work its magic out of anything shorter than 14 inches? Correct me if I'm wrong. What magic?? 55gr XM193 bullets tumble when they hit a soft target, because the rear of the bullet is heavier than the front. If the bullet is above a certain velocity when it hits the target, the thin-jacketed bullet used in the XM193 load cannot sustain the pressures created when the bullet turns sideways a couple of times, so the thin jacket breaks, and the soft lead will violently erupt and fragment, creating very effective ballistics. If the bullet is traveling below that velocity, the chances that the bullet will fragment go way down, and the ballistics aren't so impressive. A 14" - 15" barrel is needed to get the XM193 to reach that velocity. If the barrel is too short, like a 9" pistol barrel, you'd be better off using a heavier bullet. That's what I remember about that cartridge. If I'm wrong about any of that, feel free to correct me. The XM193 is my favorite cartridge for my carbine for various reasons, but I've been told that a pistol will be more effective with a heavy load. Sir, we are not Hague Convention bound for civilian use, including home defense. M193 and M855 are very poor choices for civilian use. You want soft point bullets or expanding monolithic bullets, yes, even in short barrels. Something like the 64 grain Speer Gold dot, or the 53, 55, or 62 grain Barnes TSX. All of these bullets will expand well at pistol velocities and are far more effective than Hague Convention compliant military ammo. |
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Posted: 8/29/2014 1:16:24 PM EDT
[#31]
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Sir, we are not Hague Convention bound for civilian use, including home defense. M193 and M855 are very poor choices for civilian use. You want soft point bullets or expanding monolithic bullets, yes, even in short barrels. Something like the 64 grain Speer Gold dot, or the 53, 55, or 62 grain Barnes TSX. All of these bullets will expand well at pistol velocities and are far more effective than Hague Convention compliant military ammo. Well, that's news to me! I thought the XM193 was great for self defense, at least out of a 16" barrel. That's what's been holding me back from getting a pistol or SBR for a while now. |
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Posted: 8/29/2014 2:11:32 PM EDT
[#32]
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Well, that's news to me! I thought the XM193 was great for self defense, at least out of a 16" barrel. It's not, out of any barrel length. Frankly, IMO the 223/556 cartridge out of a 7" barrel is an utterly ludicrous concept for any practical application. If I wanted a 7" barrel firearm I'd pick a cartridge more suited to a 7" barrel, like maybe 9mmP or 45acp. |
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Posted: 8/30/2014 11:52:18 AM EDT
[#33]
1:9 is the best overall barrel for most shooters.
If you are only punching holes in paper with bullets above 69 grain, I would recommend 1:7. 1:7 twist was designed specifically by the Army for the 62 grain bullet, but it does not work as well with 55 grain ammunition, which is the majority of what is sold inexpensively, and what most scopes, (Nikon, etc), that are made for the .223 are calibrated for. 1:9 is the best overall compromise for most applications. |
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Posted: 8/30/2014 12:33:44 PM EDT
[#34]
So I have a 7.5" pistol with a 1:9 twist...shooting inside 100yds...what is my best stopping round? Heavy soft nose or heavy hollow point? Or....something much lighter?
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Posted: 8/30/2014 12:45:54 PM EDT
[#35]
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So I have a 7.5" pistol with a 1:9 twist...shooting inside 100yds...what is my best stopping round? Heavy soft nose or heavy hollow point? Or....something much lighter? If I could, I would want to use a slightly longer barrel length to burn more powder before the bullet exits the barrel, thus increasing velocity. I am not sure what the ideal short barrel length is for .223/5.56. I just purchased a 10.5" in .300 blackout as shorter lengths do not fully take advantage of the propellant. But to your original question, I would try a heavier bullet. I would do my own tests to determine what expansion you may expect with either lead nose or some sort of hollow point. If I had to pick right now, I would go with lead nose as I have seen the effects of that on flesh and it will penetrate clothing and still do some damage. |
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Posted: 8/30/2014 1:16:14 PM EDT
[#36]
A person must have a twist rate that stabilizes the ammo with longest bullet that will be used.
AFAIK 1:7 was adopted based on FN’s recommendation for what is needed to stabilize the bullet used in M856 tracer ammo. M855 ammo works well with 1:9. |
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Posted: 8/30/2014 1:40:20 PM EDT
[#37]
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1:7 twist was designed specifically by the Army for the 62 grain bullet Quote HistoryQuoted:
1:7 twist was designed specifically by the Army for the 62 grain bullet No, it wasn't. 1:9 was the original twist rate used with the M855 "62gr" bullet, which is roughly equivalent in size to a 71gr lead core FMJ (also where the 68 & 69gr OTMs came from). Twist rate was increased to 1:8, then 1:7, to meet a specific accuracy requirement with the very long M856 tracer in arctic cold temperatures. 1:9 is the best overall compromise for most applications. "Best" would probably be 1:8.5. Before the advent of the 80gr Sierra, there were some 1:8.5 barrels made for the 75/77gr OTMs. 1:8 would be the closest that's currently available. |
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Posted: 8/30/2014 1:52:42 PM EDT
[#38]
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1:9 is the best overall barrel for most shooters. If you are only punching holes in paper with bullets above 69 grain, I would recommend 1:7. 1:7 twist was designed specifically by the Army for the 62 grain bullet, but it does not work as well with 55 grain ammunition, which is the majority of what is sold inexpensively, and what most scopes, (Nikon, etc), that are made for the .223 are calibrated for. 1:9 is the best overall compromise for most applications. 1/7 was specifically adopted to stabilize M856. ETA- gamma beat me to it like usual
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Posted: 8/30/2014 7:10:30 PM EDT
[#39]
So 1:7 doesn't work well with 55gr because it over-spins the round, right? I've heard that this can actually cause a weak-jacketed 55gr to air-burst, is that real?
1:7 is bad for 55gr in a carbine length, but it would be ok in a 7.5", at least up to 100m, right? Because the bullet isn't getting up to such a high velocity, and thus a lower spin rate, right? What are 69+gr bullets like out of a 7.5" 1:9? |
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Posted: 8/30/2014 11:35:03 PM EDT
[#40]
I have a 1/7 that shoots the 52's really well. And they're not flying apart. That is only a concern with perhaps some of the lightest bullets. I've even shot umc 45 grain bullets in my 1/7 and they grouped rather decently and didn't appear to make any weird looking holes in the paper.
I only have experience with 14.5" and longer. The rifle I was referring to above is a 20" barrel. But I have not found the lighter bullets to be a problem in any 1/7 I've shot or owned. The lighter bullets being overspun is an exaggeration, in my experience. There may be some truth in theory, but not with 55's. As I said, maybe some super light bullets. There have been a few reports on here of this. |
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Posted: 8/31/2014 12:26:50 AM EDT
[#41]
Bullet RPM is determined by velocity and twist.
So change velocity significantly and you have also changed bullet RPM significantly. I have seen the occasional post about problems with M193 with 1:7 twist rifles at longer ranges. |
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Posted: 8/31/2014 2:05:28 AM EDT
[#42]
Its my personal belief that this is all theory, but not fully proven. Standard Mil M4 barrels (14.5" 1/7) stabilize both the M193 (55gr) and MK262 (77 gr) bullets very well, but groups open up when firing issue 62 gr M855 green tip. Supposedly a 1/8 twist is the preferred rate for the 77grain, and my Larue 16" stealth (which has a 1/8 Lothar) prints sub MOA groups with the MK262. But I also have a "garage built" AR with a 20" 1/9 E.R. Shaw that also shoots sub MOA groups with both the MK262 as well as the Hornady 75gr BTHPM. Also, another "garage build" sporting a 16" 1/9 DPMS barrel (I think I paid $160 for this barrel from Brownells a couple years back) I have will print MOA with the same 75 gr BTHP match, and 1.5 MOA with M193. This isn't theory, this is actual performance of rifles that I have. I will add that all of the rifles I've mentioned have some type of "free float" tube, with the exception of the Mil rifles. Its my opinion that the quality of the ammunition and the quality of the barrel play a larger role in the performance of an AR type rifle than the actual twist rate, at least from the standpoint of accuracy and stabilization, and assuming the capability of the shooter is at least equal with the capability of the rifle.
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Posted: 8/31/2014 8:57:29 AM EDT
[#43]
ALL spitzer-style bullets WILL tumble on impact. PERIOD. How much and how quickly depends on velocity on impact and bullet length. A standard 55gr FMJ bullet will tumble on impact no matter what. But out of a 16" barrel at "home defense" distances, it has enough punch to go straight through a lot of tissue before it tumbles. Out of a shorter barrel, it may not be quite as energetic, but it will still have lots of energy in less than 100 feet from the muzzle and that probably will prevent it from doing a good job of tumbling on impact.
For home defense, I personally don't think an AR is a good choice. Unless you're HIGHLY trained in indoor employment of a rifle, the size of the rifle gets in the way. Again this is MY opinion... For home defense, a .45 ACP pistol strikes me as a much better choice; pointing is more like pointing your finger, and it's more than powerful enough to stop a man if you hit him at all. OP, the practical difference between 1:7, 1:8, and 1:9 twist is so minor as to be almost entirely meaningless. For longer distances, you want heavier bullets, which retain momentum and are less affected by wind, and heavier bullets are longer. Faster twist works better with heavier, longer bullets, BUT a 1:9 twist isn't going to keep a quality bullet from maintaining stability at fairly long ranges. And you will find that two identically spec'd barrels will perform differently with identically spec'd rounds...so if you like the 1:9 barrel for everything else about it, try it out. The potential difference in "stabilizing heavy bullets" between 1:9 and 1:8 is infinitesimal at best, unless you're trying to use 130 grain bullets!
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Posted: 8/31/2014 11:03:26 AM EDT
[#44]
Ive heard 1-9 can usually stabilize up to 65gr
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Posted: 8/31/2014 11:22:19 AM EDT
[#45]
Topic Moved
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Posted: 8/31/2014 3:04:53 PM EDT
[#46]
Quote HistoryQuoted:
Ive heard 1-9 can usually stabilize up to 65gr 1:9 is the optimum twist for up to the low 70s grain weight in typical lead core bullets, to include the 68 & 69gr OTMs, the Berger 73gr OTM, and M855. It's marginal with 77 & 75gr OTMs. Weight in and of itself is meaningless to twist requirement for stability, it's the length, center of gravity, and shape of the bullet that matters. But bullets are commonly just referred to by their weight so hard to describe things correctly. |
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Posted: 8/31/2014 3:15:24 PM EDT
[#47]
Quote HistoryQuoted:
1:9 is the optimum twist for up to the low 70s grain weight in typical lead core bullets, to include the 68 & 69gr OTMs, the Berger 73gr OTM, and M855. It's marginal with 77 & 75gr OTMs. Weight in and of itself is meaningless to twist requirement for stability, it's the length, center of gravity, and shape of the bullet that matters. But bullets are commonly just referred to by their weight so hard to describe things correctly. Quote HistoryQuoted:
Quoted:
Ive heard 1-9 can usually stabilize up to 65gr 1:9 is the optimum twist for up to the low 70s grain weight in typical lead core bullets, to include the 68 & 69gr OTMs, the Berger 73gr OTM, and M855. It's marginal with 77 & 75gr OTMs. Weight in and of itself is meaningless to twist requirement for stability, it's the length, center of gravity, and shape of the bullet that matters. But bullets are commonly just referred to by their weight so hard to describe things correctly. Made perfect sense to me. Bullet length to rifling twist = effect on stability as opposed to bullet weight to twist. |
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Posted: 8/31/2014 3:33:06 PM EDT
[#48]
From my research, 20" 1-8 seems to be a good length without being too cumbersome, and the 1-8 twist is good for >60 gr match ammo that is made for longer ranges. I just got a WOA 20" 1-8 varmint barrel. I haven't test driven it yet (no optics lel), but others have called it a tac driver.
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Posted: 8/31/2014 3:34:39 PM EDT
[#49]
Quote HistoryQuoted:
Made perfect sense to me. Bullet length to rifling twist = effect on stability as opposed to bullet weight to twist. Quote HistoryQuoted:
Quoted:
Quoted:
Ive heard 1-9 can usually stabilize up to 65gr 1:9 is the optimum twist for up to the low 70s grain weight in typical lead core bullets, to include the 68 & 69gr OTMs, the Berger 73gr OTM, and M855. It's marginal with 77 & 75gr OTMs. Weight in and of itself is meaningless to twist requirement for stability, it's the length, center of gravity, and shape of the bullet that matters. But bullets are commonly just referred to by their weight so hard to describe things correctly. Made perfect sense to me. Bullet length to rifling twist = effect on stability as opposed to bullet weight to twist. Precisely. Long and skinny needs faster than short and stubby. That's the easy part. Looking at a bullet and seeing where it's CG is isn't easy. You sort of get a feel for CG location from the bullet's Ballistic Coeficient, but for most people that's just as much black magic as all the rest of internal and external ballistics is. For fancy bullets, the bullet maker should recommend a twist rate in their loading data for their bullets. Berger has something that's pretty close to that, their Twist Rate Stability Calculator lets you plug in bullet parameters and get a good idea of how well a given twist will stabilize the bullet, along with recommending a minimum twist rate. Great stuff for those of us who want to get things just right. |
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Posted: 8/31/2014 4:05:35 PM EDT
[#50]
Quote HistoryQuoted:
So 1:7 doesn't work well with 55gr because it over-spins the round, right? I've heard that this can actually cause a weak-jacketed 55gr to air-burst, is that real? Quote HistoryQuoted:
So 1:7 doesn't work well with 55gr because it over-spins the round, right? I've heard that this can actually cause a weak-jacketed 55gr to air-burst, is that real? Bullet disintegration is mostly with the very light ~40gr type varmint bullets. I've seen it myself with hot loaded 40gr bullets. In the M16A2 development program, when they went from 1:8 to 1:7 twist to try to get their M856 tracer to meet a particular spec, they found that M193 would no longer meet accuracy specs. Instead of trying something intermediate, that failure was deemed to be acceptable. Many years ago, Colt changed out a whole bunch of 1:7 rifles (to 1:9) that had been delivered to NYPD which wouldn't perform adequately with their chosen lighter weight duty load. Yes, very high quality "match" projectiles will do better with excessive stabilization than will lower grade projectiles. Excessive twist rate exacerbates any flaws or eccentricities in the projectile or other factors. It also increases downrange BC since the bullet is less able to follow it's trajectory, so very long range ballistics suffers. The faster you go in twist, the more likely you are to see detrimental effects, which is why high precision shooters tend to shoot the slowest twist that will adequately stabilize their bullets. There's a lot of discussion in this archive thread which explains some of the intricacies of external ballistics. Let's just say that the often repeated mantra of "no downside to excessive twist" is not exactly correct. http://www.ar15.com/forums/t_1_5/1578254__ARCHIVED_THREAD____Bullets_accurate_at_600yd_but_not_100yd_.html&page=1 Personally I found 1:7s to be somewhat annoying, where I'd shoot many donut looking groups but could never seem to get bullets in the center of a group, particularly at shorter ranges. The information in the thread I just linked explains why that happens. I notice much less of that with 1:8 and 1:9 barrels. I've been very happy with 1:8s. That's just my anecdotal experience. 1:7 is bad for 55gr in a carbine length, but it would be ok in a 7.5", at least up to 100m, right? Because the bullet isn't getting up to such a high velocity, and thus a lower spin rate, right? What are 69+gr bullets like out of a 7.5" 1:9? Frankly I really don't know why you'd want to shoot 77gr match loads out of a 7.5 inch barrel. Then again I don't know why folks want 7.5" barrels in 223/5.56 to begin with. |
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