I have a CVA Stag Horn and also a Stag Horn Mag, both of these MLer's are INEXPENSIVE, one was $89. I doubt one could find a Mler for less that was new in the box.
I managed to get 1 1/2" groups out of this one at 100yds. So for me I cant say the CVA Optima cant shoos, I dont have one but all I own are CVA's and all are Shooters.
I see your a New Member, are you also pretty new to Mling? Now I've been tryong to figure put your problem but 2 things hinder my findings, the Optima and the T7 Pellets, I use neither. But since your new to MLing (If you are) are you making sure the Bullet is seated Firmly on the Pellets (without) Crushing them? Another thing that may be the problem is the 1X Scope, I like a Higher Magnified Scope for shooting Longer Yardages. Do you have a Good Solid Rest, Bench to shoot off from? Are you using the right (Loading Jag) for your Bullets? And Yes keeping the Breech Plug Clean also makes a Big Difference.
Now Im a Simple Shooter, Im not into all the New Powders and Bullets, I use what works and stick with that. I own and Shoot only CVA MLer's and None have ever shot groups like you describe, and as I said even the $89 Stag Horn will shoot. Now most know this and Im Not Pushing them on you but out of all My CVA's I use the 240gr XTP Bullets, either Win W209 Primers or T7 Primers with either the (regular) Pyrodox Pellets 2-50gr or Pyrodox Powder 110gr's. And they All Shoot Acceptable Groups out to 100yds and Further. This is just a Suggestion as it's what works for me out of My CVA's.
Rifles and Mlers are Not Created Equal, long from it. You must find what your Mler like's to shoot and once you do you'll be hammering the Bull at 100. If nothing works then I would try Lose Powder and start off at about 80 gr's and work your way up untill you have the Groups your looking for.
Best of Luck to You!
(BP)