Of course CVA is going to suggest a Powerbelt. They sell them. There are better bullets out there that for something like an elk can and will do a better job.
Since you need to shoot a conical bullet. I would contact Thor Bullets. https://thorbullets.com/ The Thor is a Barnes bullet but made to conical specifications. They make them in various dimensions from .500 to .505 I believe. If you contact them they will send you a sample pack. Also their all copper design will mean excellent fight trajectory and expansion in game. This will bring down your elk. Now granted they cost a little more. But for a once in a life time hunt, you'll feel really stupid if you blow your chance or wound a trophy bull because of a couple bucks.
Others owning the CVA line of rifles report excellent accuracy with the Thors. I will contact some of them and see what diameter they shoot out of their CVA Optima rifles. This will help if you decide to order them. What model CVA do you have. One particular person I talk to shoots all makes and models of CVA and lives in Colorado. He shoots Thors.
Something I do when shooting to see what bullet and load works for me. And when Bullets are expensive. Leave the scope on for the time being. Once you have a good bullet and load. Take it off and then sight that known load to your sights. It saves time and money.
In my Optima I have shot Thor bullets. I used 100 grains of 3f Black Powder and the following bullet. With a scope I was shooting 2-2+ inch groups at 100 yards. Plenty good for a bull.
300 GRAIN BALLISTIC TIP 50 CAL - .502 DIAMETER
$26.00 + S&H
Good luck on your hunt.
"Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, a total wreck with a big smile on your face."