I see nothing wrong with shooting any animal on the run with a rifle. I have no clue how many deer I've killed with a rifle, I'll guess in the upper 50s or so, and I'd say about 20 of them were running when I shot them. I shoot my deer rifle a few hundred times during the year, I know where it shoots, and I know how to make a 1 shot kill on a running animal. I usually use jackrabbits in the summer/fall as my running shot targets. I shoot at 'em while sitting and intentionally miss them, then when they are running I shoot them. I suppose that is un-ethical too....