New to air guns. I have a FX impact M3 30 cal with a 700mm barrel. I ordered a 30 cal 700mm carbon fiber sleeve. Installing it was easy until I tried to insert it into the barrel. It will not fit. I have watched several videos and it just slides in. The sleeve OD is almost the same as the barrel OD. I think I measured the ID of the barrel on the threads at .459 and the OD on the sleeve at .464. Has anyone had this issue.