Barrels 101

[Onyx Z]

That is correct. 1/7 is sort of a catch all for heavy bullets in the 70 gr range and above and works with bullets on down to 55 gr. Less than 55 gr though and you're approaching the threshold of over-stabilization

That's why I prefer 1/8 twist. They can handle the whole spectrum of mag length loads. My precision barrel is 1/8, but it's pretty tough to find a chrome lined 1/8 barrel for some reason.

[MistWolf]

That is NOT correct. Bullet weight has little to do with the twist needed to stabilize the bullet. It's bullet LENGTH. A short round nosed bullet can weigh as much as a long pointy bullet and need less twist to stabilize. A bullet with a lead core will weigh more than a bullet of the same shape made of solid copper and both will need the same twist

[jstone]

That is correct. 1/7 is sort of a catch all for heavy bullets in the 70 gr range and above and works with bullets on down to 55 gr. Less than 55 gr though and you're approaching the threshold of over-stabilization

Bullets are either stabil or they are not. You can cause a bullet to break up from to fast of a twist rate in a barrel. But you can not over stabilize a bullet. Over stabilization is an oxy moron.How can something be to stabil.

[markm]

That's why I prefer 1/8 twist. They can handle the whole spectrum of mag length loads. My precision barrel is 1/8, but it's pretty tough to find a chrome lined 1/8 barrel for some reason.

You should be looking at SIONICs, MAMA!! That's their barrel.

[Onyx Z]

That is NOT correct. Bullet weight has little to do with the twist needed to stabilize the bullet. It's bullet LENGTH. A short round nosed bullet can weigh as much as a long pointy bullet and need less twist to stabilize. A bullet with a lead core will weigh more than a bullet of the same shape made of solid copper and both will need the same twist

And typically, the heavier the bullet, the longer it is... of course there are exceptions to every rule.

Theoretically, a 1/8 can shoot the longer/heavier bullets and the shorter/lighter bullets without the worry of spinning them apart. In the end, both 1/7 and 1/8 will work for what is typically put through an AR.

[MistWolf]

And typically, the heavier the bullet, the longer it is... of course there are exceptions to every rule...

The AR is not the only rifle in the world and the 5.56 is not the only caliber. A 90 gr 22 caliber bullet is longer and requires a tighter twist to stabilize it than a 90 gr 30 caliber bullet. It's not weight, it's length- or more accurately, it's the length to diameter ratio. Round balls typically stabilize with about a 1:22 twist, even the massive 4 bore throwing a quarter pound of lead. That's much heavier than a 90 gr 22 caliber bullet

[artyman]

Sorry for the intrusion…… If my memory on interior ballistics is correct, I believe its more accurately the bearing surface of the projectile, not its weight or length that would require a specific twist to stabilize. The ogive and boat tail wouldn't matter. Although I cannot reference it, I believe this is why we have the 1x7 twist for the M16 series. It isn't the M855 62 gr projectile, but rather, the M856, which is the same weight, but has a much greater bearing surface, requiring a tighter twist rate to stabilize. Hence, cross compatibility of all our ammunition across platforms- M16 series and M249 saw.

Thanks for listening.

Artyman

[markm]

but rather, the M856, which is the same weight, but has a much greater bearing surface, requiring a tighter twist rate to stabilize.

Have you ever seen one of those projectiles out of the brass? They are CRAZY long.

[lre433]

Ok. Thanks. Is there a chart somewhere that breaks down the rate of twist in relation to the weight/length or surface area of the bullet?

[lre433]

I have been trying to build my knowledge on barrels and until now, thought chrome lined was the best for durability. I have just been reading some posts about Melonite treated/coated barrels. This process seems to be gaining popularity. What can you tell me about Melonite barrels? Thanks...