This is probably one of the oldest tricks in the book but a sure fire way to ensure you get a consistent FPS from one shot to the next and also can help improve FPS if your current bucking isn’t sealing well.
The mod itself is done by using “cheap” PTFE tape which can be sourced from almost all DIY stores, on average a 5M roll of the stuff will cost you between 50p and £1 so it really isn’t going to break the bank. On a bucking I tend to do 2 wraps around where the bucking meets the barrel but PTFE tape can also be used on other sealing areas such as sniper cylinder heads, where there is a mechanical meeting I like to do 3 turns in a clockwise direction with the part facing up towards you. This ensures that when you screw it in the PTFE is being massaged into place rather than being pulled out.
Cheap, Easy and well worth doing on any and all airsoft weapons you possess whether it be AEG, GBB pistol or Bolt action sniper.