Spring or gasoline firing system? Both types get the job done via a piston that compresses air after which you can releases it with every bring about squeeze. The differences are the types of compressors that they use to power the piston. Spring-powered guns have a spring system set up, https://louisnvchm.wikicarrier.com/573271/handgun_vise_for_sighting_in_things_to_know_before_you_buy