Finally got my hands on my Airarms 410S carbine

While I have ordered some JSB exacts from Potters, I grabbed some Barracuda 21grn & some RWS hobbys from my LGS just to get out shooting.
The barracudas shoot nice groups, but the hobbys aren't anything to get excited about. After sighting in I took to some pigeons under a bridge at my uncle's farm & took out 10 of the 12 birds there with 11 shots

so the next day I did a tin penetration test at 30 yards: shooting both pellets on high power they both passed punched through the tin, but on low power they both bounced off. So the question I have is: if I'm shooting in sheds I obviously want to be using low power for the low noise and lack of penetration, but will I still have enough velocity/energy to knock the birds down? Do i need to fiddle with the fine adjustment, as so far I've just been using the main knurled silver knob to switch back and forth?
I want to get this sorted as a I've got a couple of business' lined up with sheds full of pigeons, but only on condition I don't turn their sheds into colanders!
Thanks fellas once again
