I picked up an APC .223 with the 8.75" barrel a few weeks back and it is awesome!  Super smooth and shoots average 1 moa groups with 75 Hornady and I seen Tarheel State firearms had a pair of Swiss serialized ones marked APC 5.56 with Swiss serial numbers and the 10.3" inch barrels, so I snagged them!  Kind of a weird impulse but honestly but they are sweet!  I kind of want to part with one of the 10.3"s but they are sequential serial numbers, so that is pretty cool!  I am gonna get the 10.3 out tomorrow and test a few  different ammo selections to see how she shoots.  I shot it over the weekend and it is smooth as well.  I definitely do not need 3 of them!  But I really wanted the 10.3s!  Apparently they do not sell those in the U.S. and the barrels are like 850!  

https://imgur.com/a/lkcp9bN

https://imgur.com/a/6CrNsJN