Newbie here. I've been looking at barrels and I've seen that some say they are 1:9 twist and some say 1:7. What's that all about and is either one better than the other?
Bbl twist rate determines what weight ammo your weapon will stabilize correctly.
Best way in my eyes to describe it is like throwing a football. Not enough spin and you'll throw a crappy, wobbly, inaccurate loose spiral. Enough spin and you'll throw an accurate tight spiral.
Basically the longer(and generally heavier) the bullet, the faster the twist must be to stabilize the bullet.
If the twist is too slow, the bullet will come out like a wobbly thrown football, which will hurt accuracy.
With the correct twist bullets will come out like an accurate tight spiral.
Best way in my eyes to describe it is like throwing a football. Not enough spin and you'll throw a crappy, wobbly, inaccurate loose spiral. Enough spin and you'll throw an accurate tight spiral.
Basically the longer(and generally heavier) the bullet, the faster the twist must be to stabilize the bullet.
If the twist is too slow, the bullet will come out like a wobbly thrown football, which will hurt accuracy.
With the correct twist bullets will come out like an accurate tight spiral.
1-9 is typically good for 45-69 gr. bullets. Above that you'll need the faster twists. Usually the most accurate bullet is one that is just barely stable.
If you reload you can cheat on the twist by seating the bullet further out than nom to hit the rilfeing and going to near max powder charge. this is what I did with my REM XP-100 221 fireball to shoot 62gr bullets with 15gr imr4227. The XP has a 1 in 12 twist and most loading books call for 1 in 10 or faster for bullets over 60gr.
If you're going to shoot primarily 55-62 grain bullets, and mostly 55 for economy, I'd get a 1 in 9. The barrel will last longer. If you want to set up a tack driver with the heavies, get a 1 in 7.
Read all of these threads and if you have questions after that feel free to post....
http://www.m4carbine.net/showthread.php?t=7009
http://www.m4carbine.net/showthread.php?t=7009
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