1:9 twist vs 1:7 twist?

[Burnsie]

I was looking at the AR kits at Del Ton and saw the different options for barrels. What is gonna be the main difference between the two? Velocity is affected by barrel length, right? So would the 1:7 be able to stabilize a heavier bullet? Would it be more accurate to longer distances?

[bogey1]

i think the 1-7 is for heavier bullets. i know my 1-9 on my fifty is only good for about 500 yrds or so using a 750 grn bullet, if i want better accuracy at a much greater distance i have to either install a 1-15 or use 800-1000 grn bullets.

[Fragger]

Yes the 1/7 is suppose to stabilize the heavier bullets better then say the 1/9

FWIW my DELton 16" 1/9HB is very accurate with 62gr. bullets. A bit more so then with similar grade 55gr. bullets which are pretty accurate too.

I have no intention to use bullets of 62gr. or more but If I were to handload say 75gr. bullets I would consider the 1/7 DELton HB.

[SteveWag]

For any given caliber, heavier bullets require a faster twist. In the case of the .223, 1/9 twist should stabilize bullets up to 75gr. Heavier bullets, 80 and 90 gr., require a 1/8 or 1/7 twist. Exact twist to achieve stabilization is somewhat dependent on velocity. The 75 gr. bullets are pretty good to 600 yards but to be accurate at 1000 yards you need 80 or 90 gr. Bullets. The heavier bullets are longer and have much higher B.C’s.
Steve

[TonyF]

Velocity is affected by barrel length, right? So would the 1:7 be able to stabilize a heavier bullet?

Yes.

Would it be more accurate to longer distances?

Maybe but many things can impact accuracy to a greater extent than twist rate.

My recommendation in favor of 1:7 is that it even shoots 55gr well enough for defensive purposes so the fast twist rate provides "me" with the greatest flexibility. Nothing inherently wrong with 1:9 but all my rifles and barrels except for one are 1:7.

[sluggie24]

I would say it depends on your intended use for the rifle. If you are planning on long distance competition accuracy with heavy bullet weights then the 1/7 would be the way to go. I personally have a 1/9 on mine and find it pleanty accurate with 55 - 62 gr bullets in the ranges I use it.

Decide what your primary use will be first and take it from there.......

[jpavoncello]

The rate of twist actually doesn't have anything to do with the bullet weight, but the bullet length. A longer bullet needs faster twist to stabilize it. Most of the time, a heavier bullet has a longer length, but not always.

[SteveWag]

“Jpavoncello” is absolutely correct, faster twist for longer bullets. My post assumed lead/brass bullet composition. If you are using depleted uranium (as some Marine competitors have) a faster twist is not required.
Steve

[sluggie24]

The rate of twist actually doesn't have anything to do with the bullet weight, but the bullet length. A longer bullet needs faster twist to stabilize it. Most of the time, a heavier bullet has a longer length, but not always.

You are correct. But with the 5.56/.223 bullets that the OP was asking about an increase in weight will give a longer bullet.

[Rick Thorne]

Heavier bullet equals longer bullet (In a 22 cal tube it only has one way for material to go). In a 1 in 9 barrel 75g shoot great at 600yds 1 in 7 & 8 up to 80g but won't stabilize at shorter ranges. 1 in 6 is for 90 & 100g bullets.