I'll show you how.
For $20.
And for $0.02 royalities for each round fired thereafter [;)]
Seriously...depending on what you're firing, it's pretty easy, but I wouldn't recommend doing so more than once (just to get it out of your system). It wastes ammo, it makes a lot of noise, and if you're not in a CIII-friendly state...it might get you some bad publicity. Not to mention not even God knows where your rounds will hit. Don't try it without a mountain as a backstop.
I've done it a couple times, but it wasn't worth the bother. It just cut down my shooting time, as I only have a finite supply of ammo with me when I go shooting [:)]
But, I really wanna bump-fire a C-Mag still...just, you know, cause I can. One day I should load one of mine up and try it...
Put firearm at waist, hold like you're some schmuck who likes to shoot from the hip. Hold trigger hand steady, with trigger finger sticking straight out. Don't bother to put your hand entirely around the trigger grip. It'll just screw up your wrist. With forearm hand, pull rifle forward slightly until it goes off. Repeat. If you get good at it, you can achieve a good cyclic rate (just always pull forward and let the recoil pull it backwards)...
Do not do this in an enclosed area, anywhere with other people within 1000 meters, or without a mountainous backstop.
Once again, I don't recommend doing it.