For the same bullet weight, 5.56 has a higher muzzle velocity than .223, therefore higher chamber pressure.
A .223 chamber does not like some 5.56 ammo, as leade is shorter in .223 and when a hotter 5.56 cartridge's bullet engages the closer .223 rifling, pressures can skyrocket to dangerous levels. You can run .223 in a 5.56 chamber, and a Wylde chamber can run both .223 and 5.56 ammo.
1:8 twist can run 50-60gr bullets, but likes 62-77gr for better accuracy.