Yes, but the M16 is still worlds better than the L85.
On the other hand, Stoner himself designed the AR-18 after he heard about the problems that the AR-15 was having, but the US Government wasn't interested in it.
Ironically, it was the IRA that made the AR-18 (as made by Sterling) famous.
My understanding is that Stoner utilized the direct impingement system on the M16 in an effort to minimize weight, but he had no illusions that it was as reliable as a gas piston.