Hitting a magazine against hard subject gives bullets inside a small jerk. If by any chance they got stuck together because of salt water, dirt or mud the hit made them move around and separate.<br>I still did it 3 years ago when in the Army for my 30 round M16 clips but it was more for show than anything.<br>The powder that u seen was a sulfa powder that helped to form clots and also disinfect.<br>US Calvary has some of the old field jackets for sale (www.uscalvary.com) they were replicas.