BudsGunShop.com - TCA P/H Rifle barrel 223REM 28" FB SS

Angelo, it is generally recommended that 5.56 pressure ammunition not be shot out of a .223 Stamped Barrel. I always also conferring with the manufacturer as they ultimately know their firearms capability best : Thompson Center Arms Customer Service at 1 (866) 730-1614 --- Mon - Fri: 8:00 a.m. - 8:00 p.m.

This barrel is stamped .223 and is not rated for .556 Nato pressure. But honestly there is a pretty wide range of .223 ammo available for many different purposes, but of you need a barrel that will handle 556 pressure you'll need to fi d a different one then this.
Also noteworthy if you can find a barrel stamped .223 Wylde these will also handle .556 pressures.