Alliant Reloder 10x
If this powder is available, I'd highly recommend its usage in .223 Remington application from 36 to 60 grain application, especially with a 1-in-12" twister. NOTHING I've tried can best the velocity with small rifle magnum primers. Accuracy follows velocity. A .224" 36 grain Barnes Varmint Grenade with a muzzle velocity of 3965 fps backed by Alliant 10x is extremely accurate and SAFE. Of course, you must determine the powder grain usage by working upward, half-the-fun right? Cliffy