I have found a great, easy, cheap, and very stable shooting bench plan. My buddy and I thought it up and I have used it a lot on the Prairie Dog towns. Here's the skinny:
1. Buy an el-cheapo Black and Decker workmate bench. One of the off brand ones at your local Home Depot, Lowe's, etc. I paid $15 for mine with a $5 mail in rebate.
2. Cut a piece of plywood 25"X40" with a large notch out of one corner for the old pot belly. Just kidding, but it is more comfortable to shoot with appox. 10"X16" cut out of the corner.
3. Screw two "L" shape pieces of wood underneath the plywood table top. Make sure they are placed so that the top two boards on the bench, that are moveable, open up to lock the top in place. One of the "L" boards will have to be about 12" long for clearance so that you can turn the handles.
My total cost was $10 and a little time since I always have a little extra lumber and plywood laying around. The bonus is that the bench folds up into a somewhat compact package.
I really like it and it is actually very strong for being so cheap.