25 Creedmoor

[Tmadding]

Looking at building a 25 Creedmoor with a 24” Carbon Fiber barrel. Option for twist are dependent on manufacturer. Current offerings from one is only 1/7.5 the other is 1/7 or 1/7.5 with lengthy waiting periods. When figuring everything on Berger’s twist rate calculator I maintain over 1.5 SG with either.
Thoughts?
TIA

 

[nm.otter]

SAAMI spec is 1:7.5 and works with 138gr A-tips. Is there a projectile out there that actually needs 1:7?

 

[SlimCreaper25]

Unless you plan to shoot coppers like McGuire 134, go with a 7.5.

 

[Tmadding]

thank you for the info.

 

[sierracharlie338]

I’m closer to sea level and went 7 twist after talking to my smith. It shoots the 135s lights out. Cold blooded killer.

 

[khuber84]

At the 25cm velocity, I'd go 7tw. Stepping to a short mag, I'd go 7.5tw.

 

[Tmadding]

Good to know. I’m not much above sea level either. I’m definitely on the fence trying to decide just because I may go with some of the heavier projectiles

 

[khuber84]

2800mv with a 134eldm(longest 25cal I've measured) with a 7.5tw has SD of 1.5, which is stable, but anything less than is considered to be losing % of BC till you get down to 1.3ish and then the bullet starts keyholing and going unstable in flight.

2800 with a 7tw has sg of 1.73, much more safety factor there. I've not had any issues with 134s being stable in 7.5tw, but my DA is typically 4-8k dependent on season/weather.

 

[willfrye027]

First barrel was a 1:7 twist. No issues there. Current barrel is a 1:7.5. Also no issues there and I shoot regularly at sea level have not detected any BC loss with the 134s. Pick whatever is available and don’t worry about it.