What should I look for when buying a used airgun?

Confirm overall condition, finish, and stock for cracks.

For PCPs, ask whether the gun holds air (has it been pressurized recently and held overnight?), whether it has been modified or tuned, whether the regulator has ever been replaced, and what the seller's fill source is. For springers, ask shot count, whether it has been resealed, and whether it has been tuned. For all guns, request photos of the bore from the muzzle and recent group photos at a stated distance. Ask why they are selling.