It seems as if I've lost the squishy nub on the adjustment arm. It's just black plastic and shaped somewhat like shallow "V". Would I have to buy a whole new hop-up to replace this or is it a specific part?Check that the nub is in there, most cases people lose the little squishy nub that puts pressure on the top of the BB to give it the backspin. Alternately, you could have a feeding problem.
Would any foam work? I think I still have some fairly stiff packing foam I could possibly use. I'll just have to find something to measure in millimeters around the house haha.You can fashion your own nub very easily by using Cheese Man's wonderful trick. Get a nerf dart, and cut a piece of foam off of it, maybe 10mm x 10mm long x 20 mm thick APPROXIMATELY. What I did was glue the foam to the hop up arm. That will put an even amount of pressure on the top of the bucking to provide for a more CONSISTENT backspin on the bb. This will in turn also give you better accuracy overall.
Oh okay. Does this need to be cut in a specific shape or just a rectangle?Packing foam works okay, but you want the squishyness of the nerf foam.