You should know the laws in your state, county and city and fully comply with them. This may only be some of the state and local restrictions governing Airguns and Airsoft guns:

No Airguns or BB guns should be shipped to addresses in Washington, DC.

No Airguns or BB guns should be shipped to addresses in New York City and its boroughs: Manhattan, Brooklyn, Bronx, Queens and Staten Island. The NYC zip codes affected are: 100xx-104xx, 111xx, 112xx-114xx, 116xx.

No Airguns or BB guns should be shipped to addresses in Chicago, IL

Residents of IL should not bid on Airguns  that are 700 fps or higher or Airguns that are over .180 caliber.

Residents of New Jersey should not bid unless they have an Airgun permit

Wording from New Jersey law: "A 'firearm' means any handgun, rifle, shotgun, air gun, gas gun, machine gun, or 'any gun.'"

Residents of Michigan may bid on anything except pellet guns measuring 30 inches or less (overall length) Like pistols. Unless there is no rifling in the barrel

Johnson City, Tennessee: No Airguns, Airsoft guns or slingshots can be shipped.

 

Personally I have used the USPS service, but

Mainly I use Fed-Ex or UPS to ship, with no problems, but I don't use the phase Gun in my  discussions.