http://blogs.findlaw.com/blotter/2014/08/5-bb-gun-laws-you-need-to-know.html#sthash.BIwB6wMQ.dpuf
"What are the laws regarding BB guns? Here are five you need to know:
1) BB guns aren't required to have orange-tipped barrels. Under federal law, imitation firearms are required to have blaze orange barrel tips. But the statute specifically exempts "traditional BB or pellet-firing air guns" from the requirement.
(snip)
3) There's a difference between BB guns and Airsoft guns. Although, like BB guns, Airsoft guns are manufactured to look like real weapons and use air pressure to fire a projectile, the difference lies in the type of projectile fired: Airsoft guns fire plastic projectiles while BB guns and pellet guns fire metal projectiles. The two are therefore often subject to different laws. For example, Airsoft guns are required by federal law to have the same orange-tipped barrels as toy and other imitation guns."
Goes on to say that two states (New Jersey and Rhode Island) treat BB and pellet guns as "firearms" while NYC requires a license to possess or sell them.
The relevant federal law that expressly exempts BB and pellet guns from being required to have the orange tip signifying they are a toy:
http://codes.lp.findlaw.com/uscode/15/76/5001
Further:
http://wdtn.com/2014/10/06/why-bb-guns-are-not-required-to-have-orange-tips/
(snip)
Centerville gun shop owner John Thyne says they should be considered weapons.
"They can cause bodily harm. They can actually kill someone if its hit in the right location," said Thyne.
He says there are not a lot of laws when it comes to BB and pellet guns although many cities have codes that dont allow them to be shot off in town.
Natalie: Do you think there should be stricter rules?
"Yeah I really do. I'm obviously pro second amendment and all the stuff for personal rights but I think that gun is a weapon and there are BB guns today or pellet guns that are, in some cases, more powerful than .22s," said Thyne.
(/snip)