Prone — that is, laying on your belly — is the most stable position you can shoot a long gun from. The most body contact you have with the ground, the more stable you'll be, and in prone, nearly all of your body is on the ground. This position is used by competition shooters, target shooters, snipers and hunters, and it's worth learning how to do it properly.
Shooting from prone is a relatively simple concept — get as flat as you can, spread your legs wide and flatten your feet against the ground. This gives you a wide, stable platform and lots of body-to-ground contact. You want to utilize bone-on-ground support rather than muscle tension to keep the gun where you want it. In other words, you should not be pushing, pulling, or flexing any muscles in order to keep your eye lined up and the gun pressed to your cheek. When you're all lined up, close your eyes. Take a deep breath, relax into the ground, and open your eyes again. If you're not still on target, you have not yet achieved your "natural point of aim," and you need to move yourself around to get to the point where you can stay on target without using any muscle tension.
To achieve that, you'll need a sandbag, a bipod or another type of rest (hunters often use their backpack) to settle the forearm — never the barrel — on, which keeps the front of the gun stable. To keep the rear of the gun stable, you'll need another sandbag. A "squeeze bag" is helpful, in that it lets you adjust the height of the stock by squeezing the contents of the bag. But if time is of the essence, or you find squeeze bags cumbersome, or you just don't have one available, you can use your own hand to support the rear of the gun.
Proper Prone Demonstrated By A Pro
I recently attended a class at Gunsite Academy, where I spent several days behind Mossberg's excellent new MVP Precision rifle in 6.5 Creedmoor, ringing steel at 1,000 yards from the prone position. In this clip from that class, instructor Il Ling New demonstrates how to get set up to shoot prone without a rear sandbag for support.
