[Imperial Guard]

Thanks for the reply.
Upon a closer look, I actually found that the loading nozzle was kind of out of alignment with the hopup/inner barrel assembly. The hopup assembly was fine and I even did the seal enhancement thing (specified in the upgrade/modification section).

On the other hand, the nozzle on the cylinder head was loose (I could turn it while it should be sealed dead on). I guess that's the major source of the suspected leaking problem. I think I'll try after market cylinder set and see how it goes. I'm really hoping it's not the inner barrel/hopup chamber alignment problem.