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1:9 twist
- Thread starter Glock31c
- Start date
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Correct. 1:9 twist rate is one full rotation of rifling in 9" of barrel. So a 1:7 completes a rotation in 7" of barrel. Heavier bullets require faster twist rates to stabilize. A lot of people want 1:7 because it is mil spec but there is nothing wrong with 1:9 for 95% of shooters.
Dan1612
Master
Stick to 55-62 and you'll be fine. All of mine are 1:7 with one 1:8 (which is the most accurate), but I've never fired a bullet over 62 grains through them, so if they were 1:9, I never would have noticed. But, I prefer 1:7 in general for versatility.
Little Jack
Master
1/7 twist was selected to stabilize a very long tracer round.
Twist rate alone doesn't guarantee good accuracy. Each barrel is going to like certain rounds better than others.
I've got some 1/7 barrels that shoot 55 gr fine. I've also got a 1/7 that shots 3-4" at 25yd with 55gr. That barrel shoots 62gr fine though.
Twist rate alone doesn't guarantee good accuracy. Each barrel is going to like certain rounds better than others.
I've got some 1/7 barrels that shoot 55 gr fine. I've also got a 1/7 that shots 3-4" at 25yd with 55gr. That barrel shoots 62gr fine though.
1/9 is the most versitile twist rate for an AR, 1/7 like they said is for longer heavier bullets to keep them stable but you can still shoot tracers and 77smk out of a 1/9 barrel they just dont stabilize as well and wont be as acurate past about 100 yards, inside 100 yards m856 tracers (64gr orange tip) and 77gr SMK OTM still shoot to point of aim just dont try to use a can.
Keep in mind that velocity also plays a roll in determining the appreciate twist rate. Longer barrels will generate higher velocities than shorter barrels and as a result the rpm's of the bullet will be higher for a given twist rate in a linger barrel. If your AR has a 16" barrel it will need a faster twist than a 24" barrel will need to stabilize the same bullet because the velocity will be less.
The same goes with cartridges that fire a given bullet faster. A .223 will need a faster twist rate than a 220 swift will need to stabilize the same bullet.
Also keep in mind that the length of the bullet determines what twist rate you will need, not bullet weight. For example, an all copper 55 grain Barnes bullet is going to be longer than a lead bullet of the same weight. Copper is lighter than lead so the bullets are longer.
Bullet shape also plays a roll. A round nose, flat base bullet is considerably shorter than a boat tail match bullet of the same weight. That boat tail match bullet will need a faster twist than the round nose flat base bullet.
The same goes with cartridges that fire a given bullet faster. A .223 will need a faster twist rate than a 220 swift will need to stabilize the same bullet.
Also keep in mind that the length of the bullet determines what twist rate you will need, not bullet weight. For example, an all copper 55 grain Barnes bullet is going to be longer than a lead bullet of the same weight. Copper is lighter than lead so the bullets are longer.
Bullet shape also plays a roll. A round nose, flat base bullet is considerably shorter than a boat tail match bullet of the same weight. That boat tail match bullet will need a faster twist than the round nose flat base bullet.
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Im gonna interject here, if I may.
Most arf.com'ers will scold you for suggested 1/9, but screw them. Go to walmart, academy, gander, etc. What do you find on the shelf? 55grain cheap ammo. That is why I chose a 1/9, on purpose, gasp! I knew my purpose of use was paper poppin and knew that I didnt want to shoot the heavy expensive hunting variety rounds. I also know that most, if not all, ranges will not allow shooting of tracer rounds. For 95% of people a 1/9 twist would actually be better but many get influenced by the "big names" and the people who regurgitate what they read. Not to say the "big names" dont have a point, but many dont build/buy AR15's to be battle rifles, but rather, range toys.
Just my opinion. The 1/9 will do just fine.
Most arf.com'ers will scold you for suggested 1/9, but screw them. Go to walmart, academy, gander, etc. What do you find on the shelf? 55grain cheap ammo. That is why I chose a 1/9, on purpose, gasp! I knew my purpose of use was paper poppin and knew that I didnt want to shoot the heavy expensive hunting variety rounds. I also know that most, if not all, ranges will not allow shooting of tracer rounds. For 95% of people a 1/9 twist would actually be better but many get influenced by the "big names" and the people who regurgitate what they read. Not to say the "big names" dont have a point, but many dont build/buy AR15's to be battle rifles, but rather, range toys.
Just my opinion. The 1/9 will do just fine.
Crazydoc68
Almost a doctor
http://www.survivalistboards.com/showthread.php?p=5152555
Heres a thread with a graph as far as bulley grain size and twist rates. Not the end all but some insight. Once you click on the link scroll down a little and you will see the graph! Hope this helps.
Heres a thread with a graph as far as bulley grain size and twist rates. Not the end all but some insight. Once you click on the link scroll down a little and you will see the graph! Hope this helps.
