twist question

[mustangpd]

what is the difference in a 1 x7 twist on a barrel and a 1 x 9 twist. Which one is better?

[aliceinchains]

I need more sleep.

[Schuetzenman]

The difference between 1 in 7 and 1 in 9 is 2. :laugh:







1 in 7 is the US milspec for twist rate and it is designed to stabilize a very long tracer bullet. A bullet that is as long as a 7.62 NATO projectile. 1 in 9 is more a civilian standard and will adequately handle 52 to 69 gr. bullets. Some 75 to 77 gr. bullets if fired fast enough can be stabilized but these will be top end for pressure loads.

Most match shooters use 1 in 8 as it will handle up to and including the 80 Sierra Match King projectile and it too is the same length as the 7.62 Nato 147 gr. projectile. 1 in 7 tends to throat erode faster than a 1 in 9 or even 1 in 8 given. Something about trying to put that level of spin on a bullet accelerating from zero to 3200 fps in a milisecond. You will probably never fire a 1 in 7 enough to wear it out as we are talking 7,000 to 10,000 rounds for Chrome moly steel and possibly up to 20K for stainless.

Which is better, depends on what you plan to shoot in the weapon. If you plan to shoot a lot of 55 gr. ammo the 1 in 9 would probably be your twist. 9 will also handle the 62 gr. SS109 projectile commonly used by NATO and the US. It would also easily handle 69 gr. Sierra Match King bulllets and they do pretty good even out to 600 yards. Wind will move them around so you have to dope the wind close but good results can be had. The 77 gr. Sierra or 75 gr. Hornaday bullets would do a bit better at that distance for match shooting.

[mustangpd]

The difference between 1 in 7 and 1 in 9 is 2. :laugh:







1 in 7 is the US milspec for twist rate and it is designed to stabilize a very long tracer bullet. A bullet that is as long as a 7.62 NATO projectile. 1 in 9 is more a civilian standard and will adequately handle 52 to 69 gr. bullets. Some 75 to 77 gr. bullets if fired fast enough can be stabilized but these will be top end for pressure loads.

Most match shooters use 1 in 8 as it will handle up to and including the 80 Sierra Match King projectile and it too is the same length as the 7.62 Nato 147 gr. projectile. 1 in 7 tends to throat erode faster than a 1 in 9 or even 1 in 8 given. Something about trying to put that level of spin on a bullet accelerating from zero to 3200 fps in a milisecond. You will probably never fire a 1 in 7 enough to wear it out as we are talking 7,000 to 10,000 rounds for Chrome moly steel and possibly up to 20K for stainless.

Which is better, depends on what you plan to shoot in the weapon. If you plan to shoot a lot of 55 gr. ammo the 1 in 9 would probably be your twist. 9 will also handle the 62 gr. SS109 projectile commonly used by NATO and the US. It would also easily handle 69 gr. Sierra Match King bulllets and they do pretty good even out to 600 yards. Wind will move them around so you have to dope the wind close but good results can be had. The 77 gr. Sierra or 75 gr. Hornaday bullets would do a bit better at that distance for match shooting.

Thank you :)

[shadow65]

Schuetzenman, One of the best, no nonsense answers I've seen regarding this.