I went to Knob Creek several years ago, fired not a round, and had a lot of fun. You can attend just to see the exotic stuff shooters will bring, and the amount of ammo expended when the main line is hot.
I have been to a few subgun matches, shot, and had fun. It helps to have your own subgun for these.
Haven't shot one this year and wish I could make time.
I've also been to a commercial shoot in Minnesota where I dropped qute a bit of money, quite quickly. I got to shoot a mag or two through guns I have not seen since. I thought it was worth the expense.
A bowling pin match I used to go to had side matches with subguns. Other MGs, including a .50 cal M2 could be shot for a fee per mag or belt. Now I wish I'd shot some more of the MGs. I did shoot the .50, a FND, an M16, an Italian 9mm subgun, the Beretta 38/42, and a few others. Fun, fun, fun!
HTH.