The .223 will shoot just fine out of a 5.56 chamber , basically the same cartridge just lesser pressure , I shoot .223 ammo out of all my 5.56 barrels and it works just fineThe 5.56 is proving hard to find this week. I like to put in a good stockpile of ammo for all the calibers I own. I bought 140 .223 on Friday at $7.75/20. The same brand in 5.56 would have been 11.95/20. Why the difference? How is the .223 going to shoot in the 5.56 chamber?