sig 552 hop up: too tight!

[Rotting]

Couple things can be wrong.

Generally, the SiG552 hop-up is extremely tight even for the stock brass barrel. Which type of tightbore 6.03 are you using?

What type of bucking sleeve are you using?

The adjustment knob on the SiG552 hop-up is always extremely difficult to adjust. Personally on my SiG552, I was carrying a small screwdriver in my left hand glove to adjust it mid-game should it be necessary, however if you do not wish to do that, prior to a game you can apply a very thin layer of 100% pure silicon oil on the surface of the opening of the adjustment knob. Be sure you have a very fine film on, as otherwise you may get oil everywhere. After you've applied and attached the knob, go along the seams with a cloth and wipe around the seams just in case there's any oil peaking out, you don't want that hanging out.

As far as the rubber being a pain in the ass to get in, I used to put mine in the freezer for about 30 minutes or so and have breakfast/lunch or whatever meal I was awake for. The rubber would shrink and become a tighter fit on the barrel, and would slide in a bit easier, as well with a very small dab of lotion (If you use lotion, make sure it's not petroleum-based, as it can degrade the quality of the rubber over time).