Short stroke

Short stroke
The problem that short stroking is addressing, is that when you run a very high speed setup, your gun's sector gear may start to run so fast that it "reengages" (grabs the) piston again before it fully returns to the front of the gearbox. A shorter stroke of the piston will then make the piston get to the front faster. This enables the high speed setup of your gun to perform better, thereby also increase the ROF slightly. Remember doing this is risky and I take no responsibility!

1 How
The idea is that you want the sector gear to release the piston early. Skipping x tooth on the piston. This is done by grinding off x tooth of the sector gear. When you do this you should remove the tooth from the left (Catching) side of the gear. Removing from the wrong side will make the gun release the piston before the air nozzle is fully retracted.

2 Watch out
When you do this mod your sector gear don't use the full row of teeth on the piston. And most pistons have one metal tooth on the end. This is because the release tooth wares down quickly (10-200 shots) if it’s not made of metal. But for each tooth you take off the sector gear, the piston release tooth is also moved one tooth. There by releasing from a non-metal tooth. To fix this problem there is 2 solutions: The easy one is, by a piston with a full metal row. The hard one is to grind of piston tooth (from the front) and move the metal tooth back thereby again releasing from a metal tooth.

3 Pro / Con
Pro's: Increase ROF (1-2 RPS per tooth removed). Decrease of the load on the piston (So it doesn’t break under the stress). Decrease the impact forces pounding the gearbox (almost never a real problem).
Con's: Loss of power (FPS/MPS) 3-6 Mps per tooth removed.

4 Improvements
The loss of power from the gun can be addressed by adding power: Upgrading the spring to a more powerful one. Or adding spacers to make the piston compress more. Additionally allot of guns have holes in the cylinder. This means that the piston is not compressing air before they pass the hole. In these guns the loss of power will be minimal and you may not need to increase power.

5 Problems
When you short stroke a gun, you may encounter a problem where 2-3 rounds are shot simultaneous often under semi fire. This problem can be dealt with in two ways. The hard way is to modify (shaping) the tappet plate. The easy and still very cheap way that you should always take is just adding a "sector clip" witch is a small plastic peace that you add to the sector gear.