When lot testing some key things to keep in mind include the following.
First, wind conditions are very important. Many newer shoonless don't yet use wind flags or use them effectively. Therefore, if possible, shoot in absolutely calm conditions.
Why? Especially when winds are gusting, or switching directions, even a small amount of wind can move a standard velocity .22LR bullet enough to skew results. Every 1 mph difference in crosswind between one round and the next can cause .1" of wind drift at 50 yards.
Second, it's important to compare a sufficient amount of data (groups) to
begin to approach having
reliable data. That often means shooting enough rounds in a group and enough groups to reveal all or at least most of the variety of results with that ammo. It's much easier to shoot a very good five round group than it is to shoot a ten round group. It's much easier to shoot two good groups than it is to shoot more of them. More data (groups) are always better than fewer. Never let one or a few good groups seduce you into thinking the ammo is the one.
Third, it's important to do comparisons with as similar shooting set up as possible. For example, always use a stable bench or table. Use a good rest, always set up the same way. Ensure that the action screws are similarly torqued each time. Make sure that the hold on the rifle is always equal and consistent. Always make suree the barrel is seasoned. Don't rely on first shots from a clean bore.