I used to frequent this forum:
http://www.slinging.org/
Ballistics article,
http://slinging.org/index.php?page=t...hom-richardson
Interesting to note that 85 g lead slingshot and 40 g lead slingshot both have similar velocities (m/s):
85g: min. 29.9 avg. 31.2 max. 32.6
40g: min. 29.3 avg. 30.6 max. 32.5
compare .45 acp: (12g) (373 m/s) (835 J)
vs. slingshot: (85g) (32 m/s) (43.52 J)
momentum = M*V
85*32=2720
12*373=4476