# Barrel length and twist rate

#### mkk

##### Well-Known Member
Lets see if I can ask this question right.....

How does barrel length impact the stabilization of a bullet? Obviously a 16" barrel has 8" less influence on the bullet than a 24", same twist rate

Lets use a 105gn bullet out of a 243. 1/9 twist If I can't get it stabilized from a 16" barrel would a 20" barrel work because it was influenced by 4 more inches of rifling?

It is not so much the barrel length opposed to the twist rate. If you use the Berger Twist Rate Calculator a 105gr 6MM with a 1:9 twist is "MARGINAL". It will work.
BUT
With a 6mm 105gr you should have at least a 1:8 twist of optimal performance.
Going from a 16" to a 20" or 24" with the same twist rate will give you more velocity.
Stabilization comes more from Twist Rate and not Velocity.

Stabilization comes more from Twist Rate and not Velocity.
Very true. Very little added stabilization comes from more velocity.

So where does the rifling quit impacting bullet stabilization?

Lets see if I can ask this question right.....

How does barrel length impact the stabilization of a bullet? Obviously a 16" barrel has 8" less influence on the bullet than a 24", same twist rate

Lets use a 105gn bullet out of a 243. 1/9 twist If I can't get it stabilized from a 16" barrel would a 20" barrel work because it was influenced by 4 more inches of rifling?

Barrel length is not as important as ”twist rate”! There are some amazingly accurate handguns with barrels well under 10”. memtb

I really don't know that answer but off the top of my head I would say that in a 14 twist barrel it would be after 14".

I agree twist rate is more important, but velocity has an effect as well.
Jut go to JBM ballistic calculator and use the same bullet for different twist or different velocities. You should be able to understand it better.
Going from 20" to 22" might not be significant change in velocity, but going from 16 to 24 could be, it could be critical enough whether your bullets tumble or stay true.

Stabilization comes more from Twist Rate and not Velocity.
mkk, this is the part you need to understand.

Twist rate is generally fixed. It is displacement per turn. Example: 9" per turn.
It doesn't matter if the barrel length is 6 inches or 6 feet, the twist rate remains what it is.
Understanding 'displacement per turn' is important so that you don't end up falling for wrong thinking about stabilization.

Once the bullet has started to spin in the first few inches of the barrel it’s already at its twist rate.

@Mikecr
Does bullet RPM play a large role in stabilization.

I agree with Coyote Shadow Tracker. Barrel length has nothing to do with bullet stability. It is all about getting the optimal twist rate. A 1/7 twist rate will stabilize just about any bullet. In a 20 in barrel it spins the bullet nearly 3 full revolutions before it leave the barrel. The problem with it is it can over spin lighter bullets to the point they explode upon leaving the barrel. You need to determine the optimum twist rate for the bullet range you want to shoot and that depends on the rifles intended purpose.

I agree with Coyote Shadow Tracker. Barrel length has nothing to do with bullet stability. It is all about getting the optimal twist rate. A 1/7 twist rate will stabilize just about any bullet. In a 20 in barrel it spins the bullet nearly 3 full revolutions before it leave the barrel. The problem with it is it can over spin lighter bullets to the point they explode upon leaving the barrel. You need to determine the optimum twist rate for the bullet range you want to shoot and that depends on the rifles intended purpose.
So barrel length does impact bullet spin/stabilization

Not as much as twist rate. Velocity has a very minimal effect.

MV X 720/twist= RPM nothing in the formula about barrel length