Thanks everyone for the offers of free washers. I found someone
locally that had a spare.

Oddly the place I fill my CO2 up doesn't provide the washers, so I
never even knew I was supposed to have one. My m3 setup didn't have
instructions, so I didn't know, but at least now I do.

I also pay $22 for a refill on a 5lb cylinder, so I should probably
find another place I suppose when they don't even throw in a washer or
two, as it seems most places do.

Thanks for the help everyone.