I shoot IMI M193 (5.56) as well as my own .223 reloads. The M193 is a lot of fun to shoot. It groups well but has a slightly higher point of impact than my reloads. It is louder and has more recoil than the reloads. The good thing about it is that it is brass cased ammo so I have a source of brass as long as I still have M193 left. It's great range ammo for shooting offhand and iron sights
I take the 5.56 brass and reload it using .223 data. I can do slightly lower power reloads using less powder thus getting more "bangs" per pound of powder. With these loads at the range, they're easy to shoot and give me sub MOA at 100 yards and minute of nickel accuracy at 50 yards. I've never shot factory .223 in my AR. I do prefer my reloads in .223 over 5.56 though.
The main difference between the two cartridges is the chamber/cartridges throat, the .223 is designed to have a "tighter" fit and thus firing a longer throated 5.56 cartridge in a shorter throated .223 chamber can cause excessive chamber pressures.
That said, there is not a whole lot of difference in terminal performance between .223 & 5.56
I've got all 5.56 chambered ARs with 1x7" twist barrels. None of them seem to particularly care for 55gr .223, generally my plinking ammo is South Korean PMC X-tac 62gr SS109 type, decent accuracy, especially for plinking, and around $315 per 1000 shipped from Palmetto State Armory.
5.56 has a bit more recoil than .223 typically. You can buy military surplus rounds that have steel penetrator. If you want to go hunting us .223, you can get better rounds. If you want to carry for defense I'd personally stick with 5.56.. Designed to kill a man.
The 5.56 is loaded to a higher pressure, which does slightly increase velocity. When firing both, you can feel the increase in pressure, 5.56 compared to .223. I reload, so I stick with .223 out of my AR.
Any other reason to use 5.56 instead of .223? I just default to the milspec round because it's what I am used to and it hits a bit harder. I wonder when the new 5.56 round will hit the civillian market..
Besides a slight increase in velocity and pressure. No real advantages of 5.56 over .223. If at anytime you want match ammo, it's going to be .223. Not to mention bullet weight choice with .223.
Anyone know of any good quality 5.56 at a good price. I bought 2 30 round boxes for 10.50 a piece when I bought the gun. I think they were American Eagle by I think federal.