Given your setup, it sounds like you're doing really well. There's lots of variables there: the flexing truck hood, your knees/hips/ankles moving, your abdominal muscles moving...

I spent $40 on a plastic Predator rest, & that got me going. But going toward what, however? Well, I was able to find the ammo that my rifle likes best. In a controlled cirucumstance, after many groups, I found my gun prefers 165 grain Hornady Interbonds.

So now I've "graduated" to shooting offhand, from my knee, and with a vertical handhold on a post. If, offhand,I can get 3" at 100 yards, & 6" at 200 yards, I'm happy.

But that's just me. I'm a hunter (when I can find the time), not a benchrest shooter. I shoot a Remington, not an Anschutz. I shoot factory ammo, not reloads. I want to mount heads on the wall, not framed targets with ragged holes.

So if you want to shoot tons of tiny groups, get the lead sled. If you want to hunt, go spend the $20 on sandbags, & don't look back!

FC