I stood there for a while - thinking that there was at least another twenty minutes to wait before the chance of another shot from the same spot - and practised bracing myself against the tree with the gun. This was certainly better for steadying my aim but, even so, the sheer weight of the weapon defeated me after no more than half a minute in this position.
I picked up broken fence-post nearby and propped it against the tree. Sitting down, I found that I could use the post to both steady my arm and bear some of the weight - altogether a better position. I stayed for a while but, after all the noise I'd made dragging things around in the undergrowth, I decided that this was a spot that I'd be better off returning to another day than persevering in right then.