As used by the UKSF!
This rifle boasts Full Metal construction, an 8mm Quick Change Spring System Gearbox, a Programmable Mosfet, make this a seriously value-for-money rifle, ready at approx 330fps right out of the box, but also ripe for upgrade.

Neptune rifle from ROSSI has their latest V.2 programmable trigger, which allows semi, auto, binary and 2, 3, 4 or 5 burst fire modes out of the box.