5.56 and .223 barrels...

[aggie97]

So explain to me why some have a 1:7 twist and some have a 1:9 twist.

Looking at some of the more expensive barrels and I see most are 1:7....but there is a complete upper I have found with 1:9...and it's 800 bucks cheaper. probably a reason why it's so cheap but I'm willing to try it unless I am just barking up the wrong tree because it's 1:9.

Also, anyone have anything against stainless barrels instead of chrome lined?

Gracias!

[helosailor]

I'm by no means an expert, but I will give you my personal experiences.
I have a Del-Ton upper, 1:9, chrome lined, 16", mid-length gas system. It loves anything from 40gr up to 65gr. It performs best with 55gr. Open sight 300~350 yard are a piece of cake with cheapo 55gr ammo. Chrome lined makes it easier to clean, and I'm not sure what the advantage of a SS barrel is, other than maybe rigidity for really long shots.

[CJ]

So explain to me why some have a 1:7 twist and some have a 1:9 twist.

Looking at some of the more expensive barrels and I see most are 1:7....but there is a complete upper I have found with 1:9...and it's 800 bucks cheaper. probably a reason why it's so cheap but I'm willing to try it unless I am just barking up the wrong tree because it's 1:9.

Also, anyone have anything against stainless barrels instead of chrome lined?

Gracias!

Twist rates are exactly that, how quickly the projectile is twisted in the bore.

1:7 means 1 revolution in 7", 1:9 means 1 revolution in 9". So in other words 1:7 is a faster twist than a 1:9. Generally, the heavier a projectile is the more twist is required to stabilize it. 1:7 became the standard twist rates of M4's because of M855 ammo, which is 62gr. Previously the standard was M193 - or 55gr. A 1:9 twist can stabilize 62gr no problem, but at longer ranges it becomes less stable. Either twist is fine, 99% of shooters will never utilize a 1:7" twist. Also, as a caveat - the quicker the twist, the quicker the barrel wears out as the groves have additional lateral friction.

Stainless barrels are better than Chrome lined, they do not require any coating inside or out for corrosion, meaning they can be machined to exact specifications. Chrome lined barrels will rust on the outside, and they must be slightly over sized on the bore to account for the chrome plating. This causes the bore to be less consistent and can lead to less accuracy. You're trading reliability for accuracy, however miniscule.

[YALE]

Want to see expensive? Start pricing 1:8 twist match barrels.

[aggie97]

Twist rates are exactly that, how quickly the projectile is twisted in the bore.

1:7 means 1 revolution in 7", 1:9 means 1 revolution in 9". So in other words 1:7 is a faster twist than a 1:9. Generally, the heavier a projectile is the more twist is required to stabilize it. 1:7 became the standard twist rates of M4's because of M855 ammo, which is 62gr. Previously the standard was M193 - or 55gr. A 1:9 twist can stabilize 62gr no problem, but at longer ranges it becomes less stable. Either twist is fine, 99% of shooters will never utilize a 1:7" twist. Also, as a caveat - the quicker the twist, the quicker the barrel wears out as the groves have additional lateral friction.

Stainless barrels are better than Chrome lined, they do not require any coating inside or out for corrosion, meaning they can be machined to exact specifications. Chrome lined barrels will rust on the outside, and they must be slightly over sized on the bore to account for the chrome plating. This causes the bore to be less consistent and can lead to less accuracy. You're trading reliability for accuracy, however miniscule.

Thanks for the great info from both of you. I am going to watch the auction on this thing and see if I can snap it up. If it sucks, no biggie. The price is too good to pass up.