Here's a suggestion. I use Eley Target for practice, and Eley Club for matches. My old Buckmark Target 5.5 loves the stuff, as does my son's 2016 Buckmark Hunter.
As a competitive shooter, I care about practical accuracy, so attached is an example from last Thursday of what my Buckmark Target 5.5 can do, standing, 1-handed, at 25 yards. The X-ring on that target is 1.695" diameter.
If you care more about potential accuracy, I can tell you from past testing, that, when shooting while resting the gun on a sandbag, it makes 10-shot groups that are about 1" diameter at 25 yards. That's a good goal for a Buckmark (1" at 25yds from a sandbag), and an indication that you've found ammo that it likes. I'm sure the groups would be even smaller from a Ransom Rest.
As others have suggested, you really need to get a box of several different types of SV ammo, and test them in your gun. For example, my Target 5.5 does not like CCI SV very much, but my son's Hunter shoots it just fine.
To find ammo to test... Unless money is no object, you need to decide what your max price per round is. If you're not sure where to start, think about it this way... if you shoot 100 rounds per week, that's about 5,000 rounds per year... so what's your yearly ammo budget for this gun? Maybe start with 15 cents per round ($750 per case of 5,000 rounds), or 10 cents ($500 per case), or even 5 cents ($250 per case). Don't even look at ammo over your price limit. Use
AmmoSeek to look at each ammo manufacturer's SV offerings
that are actually for sale and in stock somewhere, to see what ammo is under your price limit. Buy a 50-round box of each type for testing. Suggested manufacturers to start with: Eley, Lapua, RWS, SK, Wolf, CCI, Aguila, Norma, Federal.
Dave