I've never seen a Sig that worked properly.
Not bashing them just stating my experience.
Just saying, the only two Sigs i've had a chance to shoot were a P226 and a 556R, the 226 was below expectations, FTE about once a mag with multiple ammo types, the Sig 556R was so terrible i was shocked it was considered a firearm, FTF, FTE, Damage to the magwell with steel mags, key-holing, stove-piping, AND the extractor would fail to hold the round and throw the casing/live round back into the action of the rifle. Almost a hilarious amount of malfunctions, loved watching the Sig rep at work dance his way around all the problems with the 556R.

MAC seemed to have all the same 556R problems we had.