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Gunsmithing Twist rates

Lrush

Sergeant
Full Member
Minuteman
Jun 2, 2012
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Alabama
Does barrel twist affect velocity?I know you need faster twist to stabilize heavier bullets.
 
A lot of br people think that a slower twist offers less resistance but I'm not sure there would be any sure way of producing clear results. It seems one can get 2 alike barrels and both not produce identical velocities.
 
So you think that if you shot an identical round out of a 308(for example)one with a 10 twist the other with a 12 twist,the 10 twist should be faster?
 
To my notion, the faster the twist the higher the pressure curve would be to accelerate the bullet. A slower twist may allow for a slightly hotter max load which should shoot a bit higher velocity.
 
So you think that if you shot an identical round out of a 308(for example)one with a 10 twist the other with a 12 twist,the 10 twist should be faster?

The 12 twist would be faster.
 
I doubt that one could measure the difference and attribute it to the twist rate.
 
The slower the twist (12 twist) will have a higher velocity than a slower 10 twist. Very, very, minimal though. I think we've tested this on a chronograph and between the two it was less than 50fps.

Ideally you want to run the slowest twist you can get away with.
 
Faster twist rates are for "longer" bullets. Heavier bullets usually are longer therefore they go hand in hand.

But take this for an example:

Take two bullets of the same weight. However is one is jacketed lead and one is pure copper. Even though they are the same weight the pure copper bullet may need a faster twist b/c it will be longer than the lead jacket bulled obviously b/c lead is denser.
That is why Barnes bullets post the recommended twists on the boxes of their bullets.

Just passing info.. Please don't take this as me being rude.
 
Faster twist rates are for "longer" bullets. Heavier bullets usually are longer therefore they go hand in hand.

But take this for an example:

Take two bullets of the same weight. However is one is jacketed lead and one is pure copper. Even though they are the same weight the pure copper bullet may need a faster twist b/c it will be longer than the lead jacket bulled obviously b/c lead is denser.
That is why Barnes bullets post the recommended twists on the boxes of their bullets.

Just passing info.. Please don't take this as me being rude.

The question didn't pertain to the stabilization and twist ratio rather the theory that a slower twist offers a higher velocity.
 
I think the simple answer is "yes", a slower twist will shoot faster if all other things were equal.

But all other things aren't equal. In fact, none of the other things are equal.
 
The correct answer is below. The lower (edited should have been lower not slower) the twist the more pressure is built up, given that all other constraints are equal. It has nothing to do with heavier/lighter bullets and stabilization as a answer.

The same applies for internal barrel finishes, the better finish the less resistance which equals slower speed. Just like a garden hose, the more resistance, the more pressure is applied to force the water at a higher speed.

Having said that, I am unsure if you could measure the difference accurate enough with getting all the other varlibles consistencly equal.

Determining your twist rate should be based on your projectile weight not speed. Everyone is always looking for more speed but remember, barrels burn out they don't wear out.
 
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The correct answer is below. The slower the twist the more pressure is built up, given that all other constraints are equal. It has nothing to do with heavier/lighter bullets and stabilization as a answer.

The same applies for internal barrel finishes, the better finish the less resistance which equals slower speed. Just like a garden hose, the more resistance, the more pressure is applied to force the water at a higher speed.

Having said that, I am unsure if you could measure the difference accurate enough with getting all the other varlibles consistencly equal.

Determining your twist rate should be based on your projectile weight not speed. Everyone is always looking for more speed but remember, barrels burn out they don't wear out.

I believe you got the first paragraph backwards. Everything I've read says slower is less resistance. Twist stabilization is based on bullet length not weight although typically these two run gand in hand but there are exceptions when bullet design is factored in.