Shorter barrel with faster twist?

[Ucsdryder]

If you go with a 19" barrel would there be any reason to increase the twist? Also, thoughts on a 7.5 twist in a 6.5cm at 5000-10000 feet? From my understanding too fast of a twist can create accuracy issues.

 

[Rich Coyle]

Too fast? Never heard of such a thing.

 

[Ucsdryder]

Too fast? Never heard of such a thing.

All of this is hearsay. So is a 1-7.5 too fast for a 6.5cm with a MV around 2675-2700?

 

[jpfrog]

Short answer- no.

That said, shorter means reduced velocity, so to combat that you'll likely want more powder with lighter pills…and you don't need faster twist for lighter pills. But it won't hurt anything.

 

[Ucsdryder]

Short answer- no.

That said, shorter means reduced velocity, so to combat that you'll likely want more powder with lighter pills…and you don't need faster twist for lighter pills. But it won't hurt anything.

Is there any calculations for that? What kind of speed difference would one expect from 1-8 to a 1-7.5? Would probably want to run 140 or 147eldm out of a creedmoor.

 

[jpfrog]

For twist rate to bullet weight calculator, a lot of people use Berger's tool online to know if their rifle's twist will stabilize their bullet. I don't know about calculating velocity for twist but someone smarter than me will chime in soon.

For an estimate of velocity, many folks say about 20fps per inch. So if a known velocity for a round on a 24" barrel is, say for example, 2700fps and you want to use the same round on an 18" barrel…subtract 120fps for an ESTIMATED velocity (6"x20fps) to get 2700-120=2580fps