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CL, no surprise. It's a 223 Rem. I broke in the barrel last night, and will probably pull it, and crown, and profile it today. And now that I've got 30 fire formed cases, I'll probably go ahead and load a few tonight.what are you building? or are you leaving it a surprise?
Yep. A flat base 60 gr lead core bullet will usually stabilize at 223 Rem velocities out of a 1-12" barrel. However, I'll probably be shooting solid copper bullets, which are longer than lead core bullets, and require a little more rpm. But even if I chose to shoot 50 gr lead core varmint bullets, a 1-9" won't over rev the bullet to the point of disintegration, like a 1-7" will. A 1-9" is about dead center for what I need here.Original SAAMI specs for the 223 Rem called for a 12 twist. That will stabilize bullets up to 63 grains. A 9 twist is only needed for the 68-70 grainers & is overkill for 55 grain bullets. Just food for thought.
Yeah, I remember in the early 80's when the 1-7" twist A2 was fielded, and then Colt introduced it commercially. Almost all bulk ammo at that time was M193 or copies (55 gr ball). I wondered why the 1-7" twist. When I joined the Army a few years later, I found out why. The M855 round with 62 gr bullet with steel penetrator needs that twist. And I was especially happy to have 1-7" M4's in Afghanistan, because I had access to 77 gr ammo.And NATO had to screw everything up with their 5.56 SAMMI specs. 58,000 psi and 1-7 twist.