Ok My Ignorance is showing again...Help please

[deerhunter61]

I have done a search for info on Barrel Twist Rates and did not find anything relevant. What I want to know is info on Twist Rates.

What is the best?

What is the difference between 1:9 and 1:14?

Why would one 22-250 have a 1:9 and another 1:14? Or would you not find this?

What or how does it impact accuacy?

How about how it would impact a 45 grain bullet and a 95 grain bullet? Does one become unstable based on the rate of twist?

Thanks,

 

[Hoppy590]

What is the difference between 1:9 and 1:14?

a 1:9 barrel makes one rotation every 9 inches
a 1:14 makes one rotation every 14 inches
obviously.

the 1:14 has a much shallower spin. generaly people say light bullets ( the 45 grain in this example) will do ok with a shallow spin, where a heavier bullet ( 95 grain) would need a tighter spin.

Why would one 22-250 have a 1:9 and another 1:14? Or would you not find this?

if you found it, its because the two guns have specific loads in mind, and are trying to optimize that loading. much like many of the AR's out there with throated barrels and Wylde chambers ( for some of the larger grain rounds)

 

[anthony-white]

The twist is how fast or slow the projectile is spun during the given distance...ie, 1:14 is one turn in 14 inches of barrel. Its effects on accuracy is in its ability to stabilize the length of a projectile (a 100 gr projectile is longer than a 55gr projectile). Therefore, a stabilized projectile will have a more consistant flight path and should yield a better shot grouping.

 

[gvnwst]

Okay, the longer the bullet, the tighter the twist needs to be for stabilized flight. For instance: .22-250 with a 40gr bullet would be good with a 1:12-1:14, but a 90gr would need a 1:7 or 1:6.5 (usually the 6.5 is specilized match barrels)
Finding the proper twist for a bullet is dividing 150 by the lenght of the bullet in thousanths of an inch, and then dividing again by the bullet diamiater (again in thousandths of an inch)
hope this helps

P.S. with to slow a twist the bullet will actually turn sideways in mid flight. imagine what this does to accuracy...
P.P.S. with a 6.5 twist and a 45gr bullet, the 45 may actually spin so fast that it explodes before hitting the target