Can you change difficulty on Spartan Ops Multiplayer

In public multiplayer, based on the experience I've had so far - the first 3 seem to be Legendary difficulty and the last 2 Heroic. Every time I play I get this same structure.

The only way to select difficulty is to start a private Spartan Ops match and you can choose the difficulty, but it doesn't appear to me that you can make it public, so you either have to go it alone (Might suit some, but I don't fancy it!) or have enough available friends.

Quite a few achievements in this game are frustrating to get because the game leans you away from the goal!

If you start a new Spartan Ops chapter it looks like there's a difficulty selector. Other than that there doesn't seem to be a way to choose.