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6mm Creedmoor barrel twist?

T

TAZMAN

Well-Known Member
Joined
Oct 23, 2003
Messages
900
Location
Indiana
I am building a new 6mm Creedmoor on a savage action that I had in the safe. I sold the barrels I had, and I am doing a 24 inch 1-7 or 1-8 twist. My gunsmith has both barrels in stock, and I will have it diamond fluted. Yes I know....why a Savage action....no one wanted to buy the gun so I am building a twin to my 308.

That being said, I have researched the heck out of the twist rates, and it appears a 1-7.5 twist is preferred for the 107-115 bullets? I have 500-105 Bergers but may switch to the 108 ELDM or something a little heavier? Is the best option just to order a 1-7.5 or stay with the 1-8 twist?
 
I am happy with a 8 twist 6 CM & shoot 105 Barnes Match Burners ( a good cheap bullet). If I wanted to include 112's or 115's I would go for a 7.5 or 7 twist. As seen below a 7.5 would do real good for 105's - 115's. I try to keep Sg values between 1.4 - 2.0. Miller sez subtract the length of the plastic tip, regarding it as weightless. Sg values calculated @ 35 F, standard pressure. A warm humid day in Indiana would boost Sg values up by 5% or so.

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The PRS competitors consume a lot of 6mm projectiles (mostly 105 or 109, some 115) in 6BR through 6mm Creedmoor. The barrels are 7 or 7.5 twist. Do not know anyone using an 8 twist 6mm barrel (maybe I run the wrong crowd). I would get 7.5 if an option or 7 with 8 twist last choice.
 
If I take the 1-7 twist, he has that one in stock. If I do the 1-75 twist, it may take a few weeks or months to get a barrel. I don't use the barrel nut system on my savage builds. I have them direct threaded with a normal lug.
 
Get the 7 twist. My two barrels I have now in 6 Creed are both 7 twist and shoot the 108 ELD-M factory ammo great and also the 110 ATip loads I have loaded up. No need to wait for a 7.5 twist.
 
I have two 6mm creeds and both of them are both 1:7 twist. I shoot the berger105 in one of them and ELD-M 108 in the other. I have tried the 110 AMAX in both and I very happy with that configuration.
 
Yep, 1-7" in mine, shoots the heavies very well.

I also did some "break in" loads with a handful of sierra 80 gr blitzkings and 90 grain accubonds I had laying around, shot those well too.
 
1-7 twist should work fine and I'd go that way versus the 1-8. Especially if you are at lower elevations, I'd err on the more twist side of things
 
I don't see much difference between the 7 or 7.5 twist except a 7 twist might be excessive for the plastic tipped Hornady 108 ELDM. On a warm day at higher elevations with lower air pressure Sg numbers will be much more than 2.0 with the 108 Hornady ELDM. Miller & other bullet wizards suggest optimum accuracy would be obtained at Sg values between 1.4 & 2.0.


The Miller process is accepted by Berger & other bullet makers. Berger uses elevation in their stability calculations and I would guess elevations in Indiana would not exceed 1,500 ft. Higher elevations result in lower pressures & higher Sg values.

Some Sg values using a 7 twist. I can get an honest 3.000 fps from my 8 twist, 24 inch, 6mm CM using the 105 Barnes Match Burner ( $0.30 each when bought by 500 bullet lots) & 40.5 grains of H4350. I use small rifle primers in my 6mm CM. At times I shoot at elevations over 5,000 ft. at temps over 80 F.

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