I'm new to this rock digging thing, and have been surprised at how _ineffective_ my grapple is at getting rocks out. Not boulders either, just big flat schist rocks lightly embedded in the field. The act of grasping the rock seems to work, but it won't lift out. Dunno yet what that's about since I'm new to this tractor stuff. I have an LA1065 loader (the 1065 is a Kilogram indicator), should be plenty of power.
What worked _much_ better on them was my combo bucket spade attached to my pallet forks. The pallet forks alone probably would have sufficed too, I just happened to have the bucket spade on them. Pried those rocks out easy as pie where the grapple would not lift them, and the bucket spade on forks must be 6 feet from the loader pin in terms of where the load is being applied. Same loader, completely different results. Losing net hydraulic energy by closing the grapple? No idea. Love the grapple, but I am repeatedly surprised how ... weak ... it is in some lifting chores. Same with turning compost heaps with my forks, though there I figure I'm just digging a little too deep.