AEG Power tuning - Install Spring, Shimming & Basic Tuning (Type: 1J)

"I bought this upgrade with an Echo 1 AK700 and I am very happy with the service I received and performance I am getting from this gun. Firstly, the work was done three days after placing my order....much faster than I expected. Secondly, the gearbox runs very smoothly so the shim job was outstanding. Thirdly, with the M120 spring I chrono'd the gun at 425 fps with 0.25 gram BBs. Thanks, Evike.