Posted: 1/9/2005 4:48:33 PM EDT
[#3]
Quoted: If you get a chromoly barrel with a 1/9 twist what grain bullet's can you use with it and what are the best one to use for that type of barrel?
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From the Ammo Oracle: Q. What twist rate do I want for my rifle?
A. Probably 1:9, but it depends on what kind of bullets you intend to shoot.
Special purpose rifles often have uncommon twist rates. For example, if you are building a varmint rifle and want to shoot the short 35 grain, 40 grain, and 50 grain bullets, a 1:12, or even 1:14 twist would be best. On the other hand, long range High Power shooters often select 1:8, 1:7.7, 1:7, or 1:6.5-twist barrels to stabilize the long 77, 80 and even 90 grain bullets used for 1,000 yard competition. Additionally, new testing of heavier rounds (68-77 grains) seems to show that they perform very well in simulated tissue and may be a better defensive choice than 55 grain or 62 grain rounds. The majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight.
1:12 twist rifles cannot stabilize SS-109/M855 bullets and 1:7 twist rifles are slightly less accurate with lighter bullets and will often blow apart the thin jackets of lightweight varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a significant amount of M856, the 1:9 twist rate is better suited for general use.
There is, of course, an exception: if you want to use loads utilizing the heavier, 75-77 grain match bullets currently used by Spec-Ops troops and other selected shooters, you'll want a 1:7 twist barrel. Although military loadings using these bullets are expensive and hard to get, some persistent folks have managed to obtain a supply, and will need the proper barrel twist to use them. Anyone who foresees a need to shoot this ammo should consider a 1:7 twist barrel.
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