Twist rate vs Altitude

[SShultz]

Hello folks,

I've been playing with the Berger calculator recently and after a brief conversation on my wanted post I figured I'd post this question up here.

I intend on building a 300 PRC.
28" barrel
Chambered for the Prec Hunter 212 eld-x.
I live at 6000 feet and hunt higher.
Shots out to a grand or more on steel, 800 is the max for game. (For now)

My instincts told me to go with a 9 twist, however at my altitude a 9 twist gives me a SG of 2.20 at my altitude on the Berger calculator. I've been led to believe that anything over 1.9 is too high. There's a slim chance that I'll hunt lower elevations in Texas. If I go with a 10 twist at sea level the bullet is marginally stable (1.45 SG). Now if I went with a 9.5 twist, the bullet would have an SG of 1.98 at my altitude, and it would only go higher if I hunt up in the hills.

What route should I be looking at? I want this rifle to shoot bug holes while I'm shooting paper and steel. Minute of vitals when I'm hunting is fine with me.

 

[sable tireur]

I live at 6,000 feet part of the year and hunt from 9,000 down to 1,400 any given hunt. I use a 1:9" twist in my 300 PRC shooting the 215 Bergers. Elk and Mule deer both die.

 

[cohunt]

i have never had an over stabilization problem-- I have heard of issues with light for caliber thin jacketed varmint bullets, but personally never seen it first hand (though I know others here have)

one thing I do know is that a faster twist rate will help the bullet on impact-- it helps the bullet expand better and it can help the bullet path stay true through the media being shot--Steve from HH recommends a higher SG too---I live at 6800, but hunt here in CO from 5000 to 10000--I like to keep the SG between 1.5 and 2, but closer to 2 if possible at my 6800 so that I know it will work well from sea level up to my max hunting altitude.

long for caliber with high BC also seems to respond well to a higher SG especially when dealing with a monolithic bullet

 

[SShultz]

Thanks for the replies folks. I suppose the next step is to sell the 10 twist barrel and buy a 9. I'm not very good at this patients thing!

 

[sable tireur]

I suppose the next step is to sell the 10 twist barrel and buy a 9. I'm not very good at this patients thing!

Put it up for sale in the Classified section here. It should sell quickly enough. Patience is a virtue. Stay calm, enjoy the experience!