How do I test a used airgun before buying?

If you can meet in person, fill or charge the gun and shoot 10 to 20 pellets from a rest at 25 yards.

Watch for consistent point of impact, smooth shot cycle, and no air leaks (a soapy water test on a PCP fill port and gauge reveals slow leaks). Cock the gun and listen for grinding, scraping, or dieseling smoke on a springer. If buying remotely, insist on recent target photos with a date marker, video of the shot cycle, and a clear return policy.