Bill - I had a 3-groove Benchmark installed on a CZ-455 Varmint Precision Trainer, which was chambered with the Lilja match reamer. It shoots very well. After the re-barrel, I tested quite a variety of different rimfire match ammo and Eley Tenex came out to be the best.
At that point, I purchased ten boxes (10 different Lots) via Killough Shooting Sports with the following criteria:
1) the manufacturer's velocity number on each successive Lot was listed at approximately 6-8 fps faster than the previous Lot. 8 of the 10 Lots actually chrono'd very close to the manufacturer's box value. In that way, I was able to cover a velocity range of approximately 1050 to 1100 fps. I then shot 4 x 5-shot groups with each Lot at an indoor 50 yd range. One Lot was the clear winner, although I don't know whether it was the specific muzzle velocity of that Lot, or the fact that it had the lowest ES by quite a bit among the Lots I tested.
2) For each of the Lots I chose, Killough's had quite a bit in stock, as I knew it would take a few days to get it tested. I eventually ordered several bricks of the one ammo that clearly tested the best.
The bottom line is that if living in Kalifornia is preventing you from doing similar Lot testing of a single specific type of ammo, chances are that you will be leaving something on the table in terms of finding the best ammo for your rifle. If you are not willing or able to have a Kalifornia store special-order exactly what you want, or drive to another state and buy it yourself, you might consider going to a test center and have them do the same thing in a much more rigorous and inclusive manner. As has been mentioned above, there is just such a Lapua test facility in Mesa, AZ:
https://www.lapua.com/resources/test-shooting/
I believe Eley also has such test centers, as well as mobile test centers, if you're interested in looking into that approach. I really think that is about the best you can do to have a rifle tested by the folks that actually make the ammo in their test facility.