A year ago I was worried about my first time shooting a 30-30, now just recently a shot a 7MM magnum for my first time. I was sighting it in for elk hunting. I was sorta worried, but I didnt get any un nessacary shakes. Same with the first time I shot a 12 Gauge (really nice pump that I use for hunting.) I was worried, but still, no un nessacary shaking. Guess its different with some people.
What Im really worried about is the .300 magnum, cant wait to get my hands on one. ;D
Anyways, on topic, if your a trained soldier, and your weapon is light, like the M16A2 or M4A1, you should have almost no shakes, unless of course your under fire, which is totally understandable. Im not sure about the no shake thing though. My dad went through SF and is retired and has showed me how he was taught to shoot, and I have no problem keeping my weapon steady, except for a marginal couple centimeter error from windage and what not.