I put a simmons 3x9 off of my 3030 and it shoot all over the place never the same place . is it wrong .?

it is a simmons 3x9 i thought it would be strong enought.it works fine on my 3030 but it shoots all over the place. one shot to the right next one to the left ,than to the top than to the right again .it is on a gamo cfx.what your thought.