If I was building a .223 bolt gun I wanted to shoot at distance I would definitely got for 1/7 as I could shoot the heavier 77 and 80 grain bullets and also have a greater OOL than the spec for a AR rifle
William is right though
for a battle rifle I would want a 1/7 but for Joe average range guy who wanted to build a pencil barrel, insert not overly accurate when compared to a dedicated precision gun, a 1/9 might just be the twist rate he/she wants
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