If a cop sees someone in full BDU walking around with what looks like a real assault weapon, the odds of you surviving that situation are not as high as you might like. Further, you may be in violation of law depending on how your gun is marked. Careless talk, by the way, will also get you in trouble. Indoor play is possible, but these BBs will break things and damage interiors so around the house is out. Care must be taken that noncombatants cannot wander into the play area for the above stated reasons.
Pistols work good indoors too.