Thanks for the advice, I got the hop-up unit separated. The bucking was so torn up, it was wedged between the barrel and the hop up ring really hard. I had to apply a lot of force.
I've got a question about the ring now. Is it common to overtorque these? Could it cause damage? I am looking at the hop-up adjustment ring and there is 1 metal tab on it and 2 parts that look like they could have been metal tabs (or maybe they are just raised areas with wear). Are there supposed to be 3 tabs? Or just 1?
See picture:
