Ideal AR barrel length

[Bloodkov]

All,

I think I'd like to get an additional upper receiver assembly for my BM AR-15 carbine. I'd like to make it a long-range plinker (fluted, free-floating barrel, flat top receiver)...

What is the ideal .223 AR-15 1-in-9 barrel length (Now that I think about it, would it be worthwhile to get a 1-in-7?) ? I know that BM makes them up to 26 inches in length but is longer better here or is there a point where it could have a negative effect on accuracy?

Does anyone know? Is there some equation out there to figure this out?

Thanks,

[Circuits]

.223/5.56mm military ammo is usually optimized for a 20" barrel.

1/9 is the best all around barrel twist, unless you plan to shoot basically nothing but very long, heavy match bullets.

1/8's just fine for 82gr match kings, 1/7 will just be more barrel wear, and less ability to shoot light varmint rounds (they can come apart in flight from the high revs).

Longer barrel length gives you a bit more velocity - although with powders optimized for a 20" barrel, they won't give you too much more.

Longer barrel length can add sight radius, although that won't matter on an AR type, since the sight base and gas port will be in the same place on a 20 through 26".

Longer barrel and more weight make your sighting plane and picture more stable, but also are more susceptible and pronounced in showing barrel droop as it gets warm.