Welcome to the GTA. Dont lose your patience with that new gun. They can be a beast to learn to shoot well. Read up on it all you can in here. We have tons of information on it if you do a few searches. They are great guns for their purpose, but not for folks that expect immediate perfection.Richard
Welcome !! Once you get the Benji NPXL1500 you can sell the gamo or send it to Ed aka Shadow on this forum for a full lube/tune, it will shoot correctly when Ed gets done for sure.
Test out a lot of heavy pellets. The magnums like the 1500 usually give their best accuracy with 10 gr or heavier pellets, as pushing a pellet much over 1000 fps usually has negative effects on airgun accuracy.
With air rifles, you usually don't want to drive the pellets over 1000 fps, even if you find the crack enjoyable. Maybe you'll get lucky and find a lighter pellet that will stay accurate at high speeds (it's been reported here from time to time), but more often than not the subpar accuracy and faster velocity loss means you can't use them at longer range, which is the whole reason for having the added velocity in the first place. The wasp-waist shape of a pellet (rather than the conical shape of a true bullet) means they usually have the best stability at subsonic speeds. But it can't hurt to try, and experimenting with different pellets is fun! Just remember to try them out at longer ranges to make sure they're still flying true.Your gun should drive a 7.9 gr lead pellet to 1200 fps, and a 10.5 gr to 1000 fps or so. And DO NOT be tempted to shoot the hypervelocity alloy pellets; they'll damage your rifle seals with time.