Any firearm chambered for .223 or 5.56mm
That depends on the type of bullet, the initial velocity, and the angle at which it is fired. A ballistics calculator is the best way to find the answer.
Yes. I own a Ruger M77 Hawkeye in 280 Rem. It plain levels whitetails out to 200 yds, with a 140 gr. bullet. My only suggestion is that if you don't reload, start. 280 Rem is not as popular as the 270 Win or the 30-06 Sprfld, so ammo is not as readily available.
100-350
You can put .223 into a 5.56mm but not the other way around due to pressure issues
Twist is 1:12
1 in 9"
1-12"
ar-15
Bullet diameter
Mine is a 1-12.
1:12 forsure