want to shoot 2 to 3 Gamo Round .22 Cal, 15.43 Grain Lead Balls in my springer

I dont think it will hurt the gun but why do it. It is not a shotgun. You will lose accuracy and FPE and possibly just injure your quarry. I say just use whats accurate to cleanly kill your game. Also shooting bb's back in the day...they are smaller than pellets and bounce down the barrel. Todays roundballs are lead and are tight fitting so the piston will have to push a lot more weight down the barrel. I always wanted to get the gamo shot shell and try that on close range pests.