BB's for air guns (NOT airsoft) only come in one size .175 commonly referred to as .177 caliber. If you want to know about airsoft BB's then you need to put the question in the "Airsoft category."
For a air soft BB gun it's okay not powerful. For a regular BB gun "NO" that is not powerful at all. A Daisy Red Ryder BB rifle will fire around 325 FPS most new pellet Air Rifles will fire at least 1,000 FPS. A really good Air soft rifle will get around 500 FPS.
500 fps
250 FPS
600 FPS - Pellet 625 FPS - BB
360 FPS
450 FPS BB 400 FPS Pellets
I believe it is about 150 fps. Which you can find on "Mini Electric " rifle. They have a - 1:3 Scale size and come in full auto. These are so much fun to use. http://www.airsplat.com/Categories/EM.htm
It was rated at 350 FPS. The same as the Red Ryder BB Rifle
FPS stands for "Feet Per Second." BB guns range from 200 FPS to around 500 FPS. Pellet guns and rifles can attain over 1100 FPS depending on the model.
70 FPS is considered low for a bb gun, of course if you were shot with it it would still hurt.
FPS depends on the type of bb used, quality of the bb, weight of the bb, and the chronograph. On top of that, it depends what shotgun it is! There are many, many airsoft shotguns out there.
For an air/piston powered .177 BB gun - anything less than 200 feet per second (fps) For a CO2 powered BB gun - anything less than 300 fps. For an "AIR SOFT" gun - anything less than 150 fps.