Range Report Twist rate
- Thread starter muleman
- Start date
Re: Twist rate
What elevation and temps are you going to shoot it at? As Rob said, some guys shooting them from 12tw 308's make it happen, though the immediate example I can think of doing that is launching them at 4500' ASL.
That makes a huge difference (appx 26-27" Hg) compared to a guy who wants to shoot them at sea level (appx 29.5-30.5" Hg).
Bob's advice on JBM is spot on as well. My personal example is the 9tw 223's that I own.
They both shoot the 75 Amax like a house on fire when the temps around me (1000' ASL) are over about 50*F but they get squirrelly and unreliable in the 40's and downright unstable by about 35F.
What elevation and temps are you going to shoot it at? As Rob said, some guys shooting them from 12tw 308's make it happen, though the immediate example I can think of doing that is launching them at 4500' ASL.
That makes a huge difference (appx 26-27" Hg) compared to a guy who wants to shoot them at sea level (appx 29.5-30.5" Hg).
Bob's advice on JBM is spot on as well. My personal example is the 9tw 223's that I own.
They both shoot the 75 Amax like a house on fire when the temps around me (1000' ASL) are over about 50*F but they get squirrelly and unreliable in the 40's and downright unstable by about 35F.
Re: Twist rate
I would say no, but measure the bullet and plug it into a calculator. My 11.25
308 is marginal with a lot of bullets at 180 grain. Running slower of coarse.
I would say no, but measure the bullet and plug it into a calculator. My 11.25
308 is marginal with a lot of bullets at 180 grain. Running slower of coarse.
Re: Twist rate
Berger says a 11 twist for their 30's over 200 gr.
I thought the 208 Amax box recommends 10 twist. Could be wrong and I know Rob01 will know that.
Is it not a lot about bullet design too? Some bullets (same weight) need more/less twist?
Berger says a 11 twist for their 30's over 200 gr.
I thought the 208 Amax box recommends 10 twist. Could be wrong and I know Rob01 will know that.
Is it not a lot about bullet design too? Some bullets (same weight) need more/less twist?
Re: Twist rate
You might get away with 210s with a 1:12 in::
a) warmer temperatures (80dF+)
b) higher altitudes (1500ft+)
The density and viscosity of air increases by 20% from 100dF to 0dF. Thus, one needs 20% more stability in 0dF than in 100dF.
You might get away with 210s with a 1:12 in::
a) warmer temperatures (80dF+)
b) higher altitudes (1500ft+)
The density and viscosity of air increases by 20% from 100dF to 0dF. Thus, one needs 20% more stability in 0dF than in 100dF.
