All things mentioned are great and will help. It is not just polishing it is remiving sharp edges and burrs. Polished against polished surface is not always a good thing, there needs a place for lubricant to be held. In a perfect scenerio a surface with slight grooves and ridges against a polished surface will give smoother and longer lasting results because those groves hold lubricant !! With no lube you end up with gaulding!
One ofvthe most difficult things to do is getting the timming correct, that is the shot cycle, the time when the pellet leaves the barrel. If the piston reaches end of stroke to soon, before the pellet leaves, a cushion of air builds up and pushes the piston back creating loss of power and what is known as piston bounce, causing a harsh recoil. Just the opposite is a pellet leaving the barrel before the piston reaches end of stroke and the piston bottoms out with no air cushion then you have a piston slam, which is very harsh and can damage the seal in a short time. Normally a loss of power also. This is where weights and shims come into play. Generally...if the piston is bouncing then extra weight is needed up inside the piston in front of the spring. This is where the difference between a steel and a plastic top hat can make a difference. The added or reduced weight changes the inertia of the piston. If the piston is slamming home after the pellet leaves the barrel then the weight of the piston needs to be lighter, removing weight of piston or removing a steel top hat and using a plastic one. After that shims should be added at the base of the spring if more spring comoression is needed. Many of todays " tuning kits" have taken this into cinsiderstion for the average rifle of a particular model. When a custom, one of a kind, tune for your particular rifle takes place, the tuner will make the fine adjustments needed with weights and shims to get that perfect shot cycle.
