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Posted: 1/20/2023 1:57:57 PM EDT
[#1]
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Posted: 1/20/2023 2:04:11 PM EDT
[#2]
Quote HistoryYou'd be surprised how many manufacturers are sticking to the slower twist rates. |
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Posted: 1/20/2023 2:57:01 PM EDT
[#3]
TLDR  
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Posted: 1/20/2023 2:58:37 PM EDT
[#4]
Slower twist rate barrels wear more slowly.
Slower twist rates are less susceptible to accuracy dispersion due to bullet or barrel defects. Faster twist rates amplify defects in barrels and ammunition. NATO chose 7 inch rifling based on recommendations from FN. The US considered other twist rates, but ultimately chose to stick with what NATO standardized. Several non-NATO countries chose slower twist rates, using similar ammo. Poland is a NATO member and chose 9 inch rifling. |
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Posted: 1/20/2023 3:08:42 PM EDT
[#5]
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Posted: 1/20/2023 3:14:01 PM EDT
[#6]
Quote HistoryQuoted: Slower twist rate barrels wear more slowly. Slower twist rates are less susceptible to accuracy dispersion due to bullet or barrel defects. Faster twist rates amplify defects in barrels and ammunition. NATO chose 7 inch rifling based on recommendations from FN. The US considered other twist rates, but ultimately chose to stick with what NATO standardized. Several non-NATO countries chose slower twist rates, using similar ammo. Poland is a NATO member and chose 9 inch rifling. There is no evidence that slower twist barrels wear slower. Barrels wear out from throat erosion. I haven't been able to find any evidence that fast twists produce greater dispersion or amplify defects. FN's recommendation was correct. 1:8 and 1:9 can't stabilize the M856 tracer in cold weather. I don't like tracers but it future proofed the rifles for newer ammo. The fact that a national military uses a feature doesn't make it a good feature. Poland, Austria et al have locked themselves out of a wide variety of bullets for no good reason. At long ranges where differences in dispersion really matter, longer bullets perform better. |
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Posted: 1/20/2023 3:26:13 PM EDT
[#7]
*It appears that some very light varmint bullets can disintegrate when fired from fast twist barrels, but I don't think these are widely available in factory cartridges. In any case, they are of no use to most shooters.
FWIW... I was taught those LtWt bullets were more of an issue when the 1n7 twist was introduced. It was because the LtWt varmint bullets available at the time were developed for use in the various 22-250 type cartridges and their slower 1n14 twists. Those thinner jacketed bullets did not play nice with the new , faster 1n7. Lots newer Varmint bullets have thicker jackets for the currently more common 1n7twist. The 1n7 even effected the 22LR bullets in use at the time ( softer lead ) , my Colt HBAR 1n7 would shoot 22LR ( with the Colt conversion kit ) about 15 ft out of the muzzle, and just go "poof" spinning apart. It was kinda interesting to watch. |
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Posted: 1/20/2023 3:30:04 PM EDT
[#8]
Quoted: Manufacturers should cease production of chrome-moly 1:9 and 1:8 barrels. It's very irritating to see an otherwise nice barrel with one of these twist rates. Why? Options is always a good thing. Btw owning AR with 3x different twist from the same mfg I have to admit that 1/9 is the most accurate of the 3 barrels using cheap 55 fmj ammo… which is the most common ammo on the market. Unless you’re building a rifle around a specific bullet for extreme accuracy barrel twist is irrelevant for the majority of internet commandos out there. This is an extremely subjective topic though.. |
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Posted: 1/20/2023 3:31:30 PM EDT
[#9]
yes
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Posted: 1/20/2023 3:35:41 PM EDT
[#10]
okay
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Posted: 1/20/2023 3:39:40 PM EDT
[#11]
I read through every bit of this a while back. Good reading.
https://www.everydaymarksman.co/equipment/rifling-twist-rate/ https://www.everydaymarksman.co/equipment/ar-15-barrel-selection/ I usually shoot what is the cheapest on the shelves. 1/8 - 1/9 was best for me. Although majority of my 5.56 guns are 1/7 |
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Posted: 1/20/2023 3:47:50 PM EDT
[#12]
Quote HistoryQuoted: Why? Options is always a good thing. Btw owning AR with 3x different twist from the same mfg I have to admit that 1/9 is the most accurate of the 3 barrels using cheap 55 fmj ammo… which is the most common ammo on the market. Unless you’re building a rifle around a specific bullet for extreme accuracy barrel twist is irrelevant for the majority of internet commandos out there. This is an extremely subjective topic though.. Optimizing for 55 grain ball? It’s not accurate in a perfect barrel of any twist. |
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Posted: 1/20/2023 3:50:25 PM EDT
[#13]
Depends on what weight of bullet you shoot, I just ordered a 1/12” because I mainly purchase M193.
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Posted: 1/20/2023 3:54:28 PM EDT
[#14]
Quote HistoryQuoted: Optimizing for 55 grain ball? It’s not accurate in a perfect barrel of any twist. 2-2.5 moa is plenty accurate for SHTF isn’t it? |
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Posted: 1/20/2023 3:59:34 PM EDT
[#15]
Quote HistoryQuoted: 2-2.5 moa is plenty accurate for SHTF isn’t it? I can get that out of 55 grain ball with any twist. I can also cut that in half with good 75 grain ammo. Why limit my options to one weight? |
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Posted: 1/20/2023 4:14:15 PM EDT
[#16]
Quote HistoryQuoted: I can get that out of 55 grain ball with any twist. I can also cut that in half with good 75 grain ammo. Why limit my options to one weight? 55gr is 90% of my ammo stash.. I’m not a long range shooter (personal preference).. in this case 55gr is perfect for me.. it’s cheap and always available.. in this case the twist doesn’t really matter.. I get 2.5 at worse with any the twist.. with the 1/9 something better. And the 1/9 can handle 75 just fine. 1/9 is not as evil as many think.. I don’t feel myself limited with it. OP stated mfg should stop making it.. that’s wrong imho. Many people cried when the ACR was released with 1/9.. but the ACR was never meant as a SPR so… |
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Posted: 1/20/2023 4:30:30 PM EDT
[#17]
I have 1/7 and 1/8...options are good. But with 55 and 62, I can't tell a difference. If I shot anything but 193 and 855, I guess I'd care.
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Posted: 1/20/2023 4:55:46 PM EDT
[#18]
Quote HistoryQuoted: Why? Options is always a good thing. Btw owning AR with 3x different twist from the same mfg I have to admit that 1/9 is the most accurate of the 3 barrels using cheap 55 fmj ammo… which is the most common ammo on the market. Unless you’re building a rifle around a specific bullet for extreme accuracy barrel twist is irrelevant for the majority of internet commandos out there. This is an extremely subjective topic though.. Let's assume that the twist rate actually is causing the difference in dispersion with the 55gr FMJ. Those bullets have such pathetically short frag ranges that it 100% does not matter. Dispersion matters when you shoot far, and 55gr FMJ sucks at distance. This wouldn't change even if you had sub-half-minute dispersion. |
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Posted: 1/20/2023 4:56:18 PM EDT
[#19]
Quote HistoryQuoted: Depends on what weight of bullet you shoot, I just ordered a 1/12” because I mainly purchase M193. You'd lose no capability with a 1:7, but you'd gain the option to use far more effective bullets. |
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Posted: 1/20/2023 4:58:02 PM EDT
[#20]
Quote HistoryQuoted: 55gr is 90% of my ammo stash.. I’m not a long range shooter (personal preference).. in this case 55gr is perfect for me.. it’s cheap and always available.. in this case the twist doesn’t really matter.. I get 2.5 at worse with any the twist.. with the 1/9 something better. And the 1/9 can handle 75 just fine. 1/9 is not as evil as many think.. I don’t feel myself limited with it. OP stated mfg should stop making it.. that’s wrong imho. Many people cried when the ACR was released with 1/9.. but the ACR was never meant as a SPR so… The 1:9 will not stabilize the bullets I mentioned in cold weather. Heavy bullets aren't just for SPRs. Bullets like the 70gr GMX and 77gr TMK outperform M193 and M855 at all distances. Why do you care so much about dispersion if you don't want any extended range capability? 55gr FMJ performs poorly at the distances where any difference in dispersion would actually matter. |
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Posted: 1/20/2023 7:56:20 PM EDT
[#21]
I don’t dive too deep into heavy bullets or special barrels. I have Colt 1/7 barrels, and my heaviest ammo is MK262.
I am friends with some pretty serious PRS shooters and gun builders and they always say any 5.56 you can load in an AR magazine will be stable in a 1/8 barrel. |
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Posted: 1/20/2023 8:17:41 PM EDT
[#22]
I think 99% of my stash is 55g or 62g. I think you aim for a stability factor between 1.5 and 2
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Posted: 1/20/2023 8:23:42 PM EDT
[#23]
Aren’t a lot of premium barrels intended for heavy bullets set at 1/7.7 or 1/7.8?
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Posted: 1/20/2023 8:52:10 PM EDT
[#24]
Both look stable to me in 1-8 twist barrels. What else you got.
Stability TMK 77 Grain Input Data Caliber:0.224 in Bullet Weight:77.0 gr Bullet Length: 1.072 in Plastic Tip Length: 0.147 in Muzzle Velocity: 2650.0 ft/s Barrel Twist: 8.0 in Temperature : 0.0 °F Pressure: 29.92 in Hg Output Data Stability: 1.623 Stability Barnes 70 grain Tac-X Input Data Caliber:0.224 in Bullet Weight: 70.0 gr Bullet Length:1.037 in Plastic Tip Length: 0.000 in Muzzle Velocity: 2650.0 ft/s Barrel Twist: 8.0 in Temperature: 0.0 °F Pressure: 29.92 in Hg Output Data Stability: 1.227 |
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Posted: 1/20/2023 8:55:24 PM EDT
[#25]
Quote HistoryQuoted: There's so much Stuck On Stupid in that I'm not even going to waste my time going through it. .... |
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Posted: 1/20/2023 8:58:40 PM EDT
[#26]
Quote HistoryQuoted: There's so much Stuck On Stupid in that I'm not even going to waste my time going through. .... ¯\_(?)_/¯ |
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Posted: 1/21/2023 12:06:35 AM EDT
[#27]
Quote HistoryQuoted: I think 99% of my stash is 55g or 62g. I think you aim for a stability factor between 1.5 and 2 https://i.imgur.com/hlvgTVi.png Stop trusting people just because they can make a chart. |
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Posted: 1/21/2023 12:26:59 AM EDT
[#28]
Quote HistoryQuoted: Aren't a lot of premium barrels intended for heavy bullets set at 1/7.7 or 1/7.8? |
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Posted: 1/21/2023 5:21:18 PM EDT
[#29]
You should post this in GD.
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Posted: 1/21/2023 5:26:15 PM EDT
[#30]
Quote HistoryQuoted: Krieger popularized that rate. Most premium are cut rifled and can guarantee that rate within 0.1". Button rifled is up to 0.8" on the slow side, in my experience. Well, I trust Krieger to be at least have a well-supported opinion. |
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Posted: 1/21/2023 6:06:25 PM EDT
[#31]
Quote HistoryQuoted: Well, I trust Krieger to be at least have a well-supported opinion. 1:7.8 - ideal for ~1.05" long 80gr. An 8 can make round holes with a even a 77gr TMK (1.07", 77gr), but BC suffers. |
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Posted: 1/22/2023 3:02:34 AM EDT
[#32]
Quote HistoryQuoted: Aren’t a lot of premium barrels intended for heavy bullets set at 1/7.7 or 1/7.8? Those are specifically geared towards the 77gr SMK, following the logic displayed in the other poster's chart. The 77gr SMK is shorter than the TMK or 70gr GMX. |
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Posted: 1/22/2023 3:11:15 AM EDT
[#33]
Quote HistoryQuoted: Those are specifically geared towards the 77gr SMK, following the logic displayed in the other poster's chart. The 77gr SMK is shorter than the TMK or 70gr GMX. 77gr SMK is the only bullet mentioned in red text in the Bible. |
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Posted: 1/22/2023 3:11:18 AM EDT
[#34]
1:7 was adopted by the military to stabilize the long tracer rounds.
1:8 or 1:9 stabilize up to 75 grain just fine, and have better terminal ballistic performance. |
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Posted: 1/22/2023 3:41:36 AM EDT
[#35]
Quote HistoryQuoted: 1:7 was adopted by the military to stabilize the long tracer rounds. 1:8 or 1:9 stabilize up to 75 grain just fine, and have better terminal ballistic performance. Monolithic copper bullets like the 70gr GMX and TSX are longer than 75gr lead bullets. Copper is significantly less dense than lead. Please show me one piece of evidence demonstrating an impact by twist rate on terminal performance. Fragmentation and expansion depend on velocity, not twist. Maybe you could get a yaw-dependent fragmenting bullet to fragment earlier in the wound track if it's on the ragged edge of stability when it impacts, but I've never seen any evidence for this. 77gr TMK is the best fragmenting bullet for 5.56mm, and it's best with 1:7. |
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Posted: 1/22/2023 3:43:04 AM EDT
[#36]
Quote HistoryQuoted: 77gr SMK is the only bullet mentioned in red text in the Bible. Sierra should discontinue it in order to produce more 77gr TMKs. The 77gr SMK had a good run, but it's quite old and the frag threshold is quite high. 77gr TMK also has a higher BC. |
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Posted: 1/22/2023 12:13:25 PM EDT
[#37]
Quoted: 1:7" is the correct twist rate because it provides almost* universal compatibility with magazine length 5.56/223 loads. There is very little evidence that the 1:8 twist produces better dispersion with medium-length bullets, as most of these comparisons seem to involve a stainless match 1:8 vs a chrome-moly 1:7. 1:8 can fail to stabilize very long bullets like the 70gr TSX, 70gr GMX and 77gr TMK in cold weather. Part of the appeal of 5.56mm is the wide availability of ammunition, and these three particular bullets are quite useful. 77gr TMK provides the best long range performance of any 5.56mm projectile. 70gr GMX is the only semi-barrier blind bullet in a widely available, full power 5.56mm factory load. 70gr GMX actually seems to be truly barrier blind, though Hornady imposes a "qualified professionals" restriction on their factory loads. Manufacturers should cease production of chrome-moly 1:9 and 1:8 barrels. It's very irritating to see an otherwise nice barrel with one of these twist rates. If someone is chasing dispersion to the point that a slow twist could even begin to be helpful, usually with 77gr SMK in a service rifle, they'll need a stainless barrel anyway. *It appears that some very light varmint bullets can disintegrate when fired from fast twist barrels, but I don't think these are widely available in factory cartridges. In any case, they are of no use to most shooters. 1:8 twist barrels are every bit as useable as 1:7 and I have never seen a reason not to use them. 1:9, while being sub optimal, is fine for a blaster rifle intended for combat style shooting using GI clone ammo (M193 - M855). A lot of internet myths exist regarding over stabilization when using faster twist rates. Using heavier bullets in 1/9 twist rates can create borderline stability and/or poor accuracy depending on individual examples. 75/77 grain match bullets just shoot better from 1/7 to 1/8 twist barrels. The couple of 1/9 rifles I own are dedicated to speed shooting drills at close range targets where high heat becomes a problem for barrel life. They get road hard and put up wet. In that role they actually shine, and they save wear and tear on my match grade barrels. |
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Posted: 1/22/2023 1:15:13 PM EDT
[#38]
Quote HistoryQuoted: 1:8 twist barrels are every bit as useable as 1:7 and I have never seen a reason not to use them. 1:9, while being sub optimal, is fine for a blaster rifle intended for combat style shooting using GI clone ammo (M193 - M855). A lot of internet myths exist regarding over stabilization when using faster twist rates. Using heavier bullets in 1/9 twist rates can create borderline stability and/or poor accuracy depending on individual examples. 75/77 grain match bullets just shoot better from 1/7 to 1/8 twist barrels. The couple of 1/9 rifles I own are dedicated to speed shooting drills at close range targets where high heat becomes a problem for barrel life. They get road hard and put up wet. In that role they actually shine, and they save wear and tear on my match grade barrels. There is no evidence that slower twist rates improve barrel life. Barrels wear out from erosion. |
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Posted: 1/22/2023 1:17:32 PM EDT
[#39]
Quote HistoryQuoted: 1:7 was adopted by the military to stabilize the long tracer rounds. 1:8 or 1:9 stabilize up to 75 grain just fine, and have better terminal ballistic performance. 1) Yes 2) Bullshit! |
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Posted: 1/22/2023 1:28:12 PM EDT
[#40]
I don't think most people care about twist rates and if they do, they probably don't even know what they got if they say, "My twist rate is the best." If they said something like, "I shoot mainly 77 gr ammo and I need blah...." then maybe take it into consideration on what they might say.
It's sort of like asking a kid if he got a tennis elbow and he tells you he likes baseball. |
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Posted: 1/22/2023 1:31:32 PM EDT
[#41]
Quote HistoryQuoted: There is no evidence that slower twist rates improve barrel life. Barrels wear out from erosion. He wasn't talking about barrel life. He's saying that he doesn't want to wear out his other match barrel when he can shoot his 1:9 barrel just fine. |
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Posted: 1/22/2023 1:33:35 PM EDT
[#42]
Quote HistoryQuoted: He wasn't talking about barrel life. He's saying that he doesn't want to wear out his other match barrel when he can shoot his 1:9 barrel just fine. Many people believe that slower twists exhibit longer barrel life. He could just as easily have gotten a 1:7 for that role, but he seems to believe that 1:9 offers advantages. |
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Posted: 1/22/2023 1:41:34 PM EDT
[#43]
But 1/9 doesn’t offer huge practical disadvantages either for the average shooter.. they shoot 55-75gr fine and that’s all that matters for most guys out there. Can’t shoot a few rounds, that’s fine.
Foreign militaries are good example as well.. or do we believe the Swiss or Austrians do not shoot long tracers in freezing temps? |
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Posted: 1/22/2023 2:10:07 PM EDT
[#44]
Quote HistoryQuoted: But 1/9 doesn’t offer huge practical disadvantages either for the average shooter.. they shoot 55-75gr fine and that’s all that matters for most guys out there. Can’t shoot a few rounds, that’s fine. Foreign militaries are good example as well.. or do we believe the Swiss or Austrians do not shoot long tracers in freezing temps? 1:9 offers some disadvantages and no advantages. Why choose it? |
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Posted: 1/22/2023 2:18:51 PM EDT
[#45]
Quote HistoryQuoted: But 1/9 doesn’t offer huge practical disadvantages either for the average shooter.. they shoot 55-75gr fine and that’s all that matters for most guys out there. Can’t shoot a few rounds, that’s fine. Foreign militaries are good example as well.. or do we believe the Swiss or Austrians do not shoot long tracers in freezing temps? 1/9 won't stabilize some 69 grain bullets. It's based on length, not weight. Why not just get the twist that stabilizes the better bullets? 1/7 shoots 55gr fine too. |
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Posted: 1/22/2023 2:35:34 PM EDT
[#46]
I've never heard of "over-twisting" a bullet other than if the rpms are too high, the bullet could blow up mid flight. See 147 grain Hornady 6.5 ELDM.
Other than that, some people believe you lose a small amount of velocity going to a faster twist than necessary. |
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Posted: 1/22/2023 2:56:12 PM EDT
[#47]
Quote HistoryQuoted: 1/9 won't stabilize some 69 grain bullets. It's based on length, not weight. Why not just get the twist that stabilizes the better bullets? 1/7 shoots 55gr fine too. If building an AR at home I’ll probably choose 1/7 of course.. as I did in the past. But 1/9 didn’t stop me from buying an AUG and will never bash Steyr for his choice since me personally I’m never gonna shoot nice ammo & I’m still able to shoot long match grade 75bthp out of it just fine. Just my .02 |
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Posted: 1/22/2023 4:18:28 PM EDT
[#48]
So, because you prefer a particular twist everyone needs to use it?
Really? Typical. Everyone needs to agree with me and everyrhing else should be banned. |
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Posted: 1/22/2023 4:40:07 PM EDT
[#49]
There is nothing a 1:8 twist can’t do that a 1:7 can.
A 1:7 can’t shoot light bullets as accurately as 1:8 can. 1:8 is the optimal choice. |
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Posted: 1/22/2023 5:14:00 PM EDT
[#50]
Quote HistoryQuoted: There is nothing a 1:8 twist can’t do that a 1:7 can. A 1:7 can’t shoot light bullets as accurately as 1:8 can. 1:8 is the optimal choice. 1:8 can't fully achieve the max BC and low temperature stability for all magazine length 5.56 loads. 1:7 can. I can't find any evidence of "excsssively fast" twist influencing dispersion. If you're trying to shoot at long distances where differences in dispersion actually matter, a long bullet like 77gr TMK is the best option anyway. |
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