I bought this from Bass Pro a few years ago, and it is incredible for the money!

http://www.basspro.com/MTM-Shoulder-...81918/-1269434

For only like $50 bucks, you get a sturdy bench rest that comes with a rear strap, so (technically) you don't really need to hold the rifle! But in all honesty, I hold down front end near the stock, just to keep it from bouncing around. I never added weights or sandbags... I guess I'm too lazy...