It's true that different ammos should be tested, but it's a bit misleading to suggest that no two rifles are the same. While bores can be sometimes viewed like fingerprints in that no two people have identical fingerprints (not even identical twins), and no two bores are identical, fingerprints, like bores, have similarities. These similarities often mean that they shoot equally similar ammo similarly. In other words, two bores can shoot the same ammo with results so similar that they seem virtually identical.
What's important is not the brand or make of ammo -- be it Eley or SK or Lapua or Norma or RWS. In the end, what's crucial is the quality of the ammo. Inexpensive or bulk .22LR ammo invariably shoots poorly. Same for high velocity and inexpensive standard velocity.
Ammo quality varies by batch or lot regardless which manufacturer produced it. For example, two different lots of any SK variety -- whether it's SK Standard Plus, SK Rifle Match or some other SK -- can perform very differently. Most will perform similarly, but some may be better than others.
The long and short of it is that every match ammo or entry level match ammo maker will produce ammo that will perform fairly well in almost any rifle.
The most productive course of action, especially at times like now when ammo availability is not good, may be to get what ammo you can that fits your budget. Don't buy ammo thinking that more expensive grades will surely outperform less expensive ones. It may happen, but it may not (especially now when the best lots of more expensive grades are almost certainly long since gone).
Don't worry about chronographing ammo. With entry level match ammos (e.g. SK, less expensive Eley and RWS), chronograph figures don't necessarily reflect performance results. In other words, good chrony figures don't always mean good results on target. Rely instead on what you see happening downrange.
