Effect of twist rate on velocity

[fusiachi]

Can anyone give me an idea of how much velocity I should expect to lose shooting the same load through a 16" 1:7 barrel as opposed to a 1:12 tube of the same length? I'm only getting 2650fps. from Sierra 55gr HPBTs over 26gr of W748 out of my Sig 556.

 

[Country]

Re: Effect of twist rate on velocity

I would think that if the barrel is the same length then not a lot off difference in velocity would be seen.
Only a chronograph could really answer this question accurately .
Faster twist rate does meam more in bore drag but it also means more pressure behind the bullet so who knows what the final velocity might be.

 

[Niles Coyote]

Re: Effect of twist rate on velocity

I dont remember my charge or exact velocity but with H335 and 55 grain spire points I get well over 2950 with a 16" 1-9 twist bushmaster.

 

[MitchAlsup]

Re: Effect of twist rate on velocity

After the bullet is engraved on the rifling, the difference in MV between a fast twist and a slow twist barrel is virtually negligible. Thus, pick the twist based on how much flexiblility you want in bullet selection.