Do you know what the sight picture is suppose to look like ?? how are you holding the pistol ?? have you had any training ?? have others shot the pistols in question ..
Something sounds fishy when you buy a gun that cheap that the person you bought it from saying he had problems with accuracy but yet shoot 6000 to 8000 rounds through it ..
and if the gun does have that many rounds through it .. it needs more service then just a new barrel .. all the springs should be replaced and a complete tear down and cleaning needs to be done ..
Have a feeling all of the story is not being told .. probably by the person that you bought from ..
here's a story where a S&W MP pistol was shot over 50000 rounds !!
pistol-training.com >> Blog Archive >> M&P Monday: Week 25