RE: cva optima pro 45cal
Assuming all is as it should be with your sights or scope and mounts, try bullets other than shockwaves and powerbelts. You say you are cleaning between shots, but are you making sure that all moisture or oil is removed prior to reloading?
You can verify that your issues are not shooter-related by shooting another gun that you know shoots well. Helps eliminate a variable anyway.
There are guns out there that just won't shoot. Maybe you have one. The odds are against that though, so I'll bet there is a load it will shoot well.
With MLs, consistency in swabbing/charges/bullets/sabots/loading/shooting technique is key.