15-20 rounds. Rifle may get jarred off zero several miles from the truck, may wound an elk and need more rounds, you never know. I have never thought to myself, "man I wish I had brought less ammo today."
A few extra is good insurance. Case in point: A few years ago I took a hard fall on shale and landed on my scope. I shot it a couple times and all seemed fine. A few weeks later, I shot an elk with it at about 200 yds. I put her down but the hit was back a ways from where I thought I'd aimed. She slid down hill in the snow and into a pile of brush. I needed a kill shot and got to about 10 yds where I could easily see her neck. It took me 4 shots to hit it, even from a good rest. I was worried that I'd run out of ammo before I got her dead.
I went through a lot of ammo sighting and resighting before I finally found the problem. I'd have it perfect then it would shift. About drove me crazy. It turned out that my fall had broken an ear off the dovetail on the back ring. I couldn't move the scope by hand but recoil could shift it just slightly, enough to throw me off about 4 MOA.
