If you have too much ammo, or too many rifles, you might be arrested….
(around here, “he was a beginner” and “underprepared”….and certainly needed more ammo….)
But in New York, he was, apparently, a serious threat…..although I doubt any of the charges stick, seeing as all the guns were legal. And Smokeless powder is a propellant, not an explosive. At best they will get him for “improper storage”.