And to the person who said I need .224 and not .223 bullets and don't ask why, I'm asking why? I like to learn as much as I can about reloading, can someone explain this to me, please?
Simple really. .223 is the caliber. Caliber is the approximate internal diameter of the barrel.
.224 is the diameter of the actual projectile. The reason the .224 is one thousandths of an inch larger than the internal diameter of the barrel is because the projectile will be able to grab (or grip) the rifling better as it's slightly larger than the barrel and because it will serve as a plug to keep the gasses from escaping past it instead of continuing to expand and accelerate it down the barrel. This is usually (but not always the case) with all projectiles (ex: the "30" caliber round is really .308, the british .303 can be .310 to .312, the .45 ACP is .451, the .270 is really .277 the 45-70 is .458. The exceptions are like the .44 magnum really being .430, not .440)
In some instances, you may actually need to "slug" your barrel, which is to say create a lead cast/mold in order measure the actual groove diameter of the bore so that you can properly size cast lead bullets that they will fully seal the bore when fired. Diameters can vary quite a bit, and "slugging" can sometimes be useful in selecting jacketed bullets for a particular barrel as well. This is usually the case with old/heavily shot barrels, although not always.
This doesn't apply to our ARs, but because you said you're interested in learning, I gave a long-ish answer, slightly off topic.
As for powders, I use Winchester 748, only because I shoot my AR quite often and prefer it's lower flame temperature (which supposedly prolongs barrel life). I also prefer not beating up the gun and cases, and W748 is rated at the lower end of the pressure chart.
However, H4895, IMR 4895 and Varget are all very good, and I've used them all. My most accurate load uses IMR XBR 8208, but that's my rifle. Yours may like a different diet.
