Why do you need to do a "finishing shot" at 10 to 15 yards? For a finishing shot, in my backyard, I use either a Beeman P17 or a Crosman 1377 and do it point blank to be sure I finish the job. Sometimes (most often now) I simply take the Benjamin Fortitude Gen2 .177 (much more quiet) and use it if I need to finish off a pest. Still at point blank to be sure.
Not criticizing, just curious.
P.S.
Although there are times I have to make a finishing shot, I try really hard to make sure the first shot does the job. Most of the time I don't need a finisher. If I start needing to use a finishing shot too often, I look at what I am doing wrong and practice to fix it. Usually it is simply lack of follow through, but it can also relate to trying to shoot too far and expect the accuracy I need/want/require.
I have trigger control pretty well worked out. It is all the other stuff that gives me fits at times. (smile)
Aim Small, Miss Small