I have a Gamo myself. Simple, efficient WTSHTF small game/keep fed tool. Pigeons and doves beware!
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If you have access to a chronograph try running a pellet in it that weighs enough that the velocity comes in under 1100 fps. I know Gamo’s selling point in many cases is that they are smoking fast but the classic, skirted diabolo pellet shape has its accuracy hammered transitioning out of supersonic.
They need to make one of those heavy duty enough to actually have “dieseling” as an undocumented feature ;-). I’ve heard they’ll get over 2k fps on a diesel but it’s hella hard on the gun!