I have one and it would be quite difficult to accurately range with it at short distances. Especially with the rear focus. I love my SWFA scope but if I were to do field target I would find a nice side focus scope.
Just for comparison, I have a 6.5-20 sidewinder and it snaps in and out of focus quickly. With my SWFA I have to go back and forth a couple times usually so I know I'm in focus. I still like the swfa more though (mostly for it's mil/mil turrets and reticle and reliable tracking), that's why the sidewinder is collecting dust.