rate of twist

[UncleWalther]

I am new to rifles, and I'm wondering how does rate of twist translate into accuracy? Does a higher rate of twist mean a more stable and consistent flight path for the bullet?

I have an HK SL8... rate of twist is 1:7. How does that compare to other rifles in the same class?

 

[HeadDamage]

It is all about the weight of bullet that you shoot. 1:7 will stablize the longer/heavier bullets like the 77gr SMK.... the 1:10 twist will not. Heavier bullets tend to be much better for long range work. BTW... NATO standard is 1:7

 

[johan]

This site explains ammo questions quite well: http://www.ammo-oracle.com/body.htm#chamb

There is a certain optimum rate of twist for the bullet weight you shoot.
Underspin and they are not in the optimum stability range.
Overspin and the projectile will be overstable and will remain pointed nose-high
Too much twist, and the bullet will fly apart.

From the site:
While the slow 1 in 12" twist is adequate to stabilize the 55 grain M193, it will not stabilize the 62 grain M855. As a result, the newer M855 ammo will group 1-2 feet at 100 yards, with bullets flying through the air sideways, instead of shooting to about 2" at 100 yards, like military ammo should.

All this has some ramifications for ammunition selection depending on your rifle's rate of twist.

When fired at 3200 fps in a 1-in-7 twist rifle, a round is rotating at over 300,000 rpm when it leaves the muzzle. Light, thin-jacketed varmint bullets (i.e., 40gr Hornady TNT or Federal Blitz bullets) often can't take that much spin and will pull themselves apart.

 

[johan]

And it goes on to suggest that for a fast rate of twist like your 1:7, a heavier bullet in the 75ish grain range is probably going to give you better results.

 

[velocity]

Wow.. you're pretty knowlegable Johan... Do you serve in the military?