1/12 twist rate and velocity question...

[TED]

I have seen that 1/9 twist barrels shoot 55gr projectiles at higher velocity than 1/7 twist barrels. This makes logical sense as the projectile spends less energy twisting and more going forward.

If that is the case is more better?

For example, if all I would ever shoot would be 55gr. projectiles, would there actually possibly be an advantage in velocity while still maintaining accuracy?

If so, does anyone still make 1/12 barrels adn in particular 16" 1/12 barrels?

Thanks.

TED

[C-grunt]

Are we sure the higher velocity was because of the twist rate and not just one barrel being faster than another?

[vicious_cb]

Theoretically this is true but chamber dimensions and ammo differences will probably have a bigger effect on velocity given 2 barrels of equal length.

[Failure2Stop]

Data does not support the original premise.

[lysander]

Less than 1% of the energy expended in the combustion of the propellant is used to rotate the projectile up the its final rotational RPM and work the recoiling parts. The changes in energy requirements to rotate the projectile to different speeds will be lost in the statistical "noise" of the velocity variation inherent in ammunition.

You won't see any velocity change due to changes in twist rate.

By the way, two-thirds, or more, of the energy produced by the propellant is wasted due to heat and other non-beneficial losses.

[Renegade04]

I have seen that 1/9 twist barrels shoot 55gr projectiles at higher velocity than 1/7 twist barrels. This makes logical sense as the projectile spends less energy twisting and more going forward.

If that is the case is more better?

For example, if all I would ever shoot would be 55gr. projectiles, would there actually possibly be an advantage in velocity while still maintaining accuracy?

If so, does anyone still make 1/12 barrels adn in particular 16" 1/12 barrels?

Thanks.

TED

As far as availability of a 16" 1/12 barrel, Brownells offer them. They are currently out of stock, but are expected to come back in stock soon.

http://www.brownells.com/rifle-parts/barrel-parts/rifle-barrels/ar-15-16-a1-carbine-barrel-1-12-assembly-prod97903.aspx?avs%7cManufacturer_1=BROWNELLS%2bMILITARY%2bBARRELS

BTW, these barrels are made by Ballistic Advantage.

[vicious_cb]

It would be foolish to limit your ammo choices for some theoretical velocity advantage. Personally I will only buy 1/7 or 1/8 twist barrels, preferably 1/7.

[Iraqgunz]

I may be totally out of my mind, but I am pretty certain that the twist rate has almost no impact at all on the muzzle velocity. I agree with vicious in that I would never purchase a barrel/upper that is going to limit ammo, unless it was type of collector deal.