This is for readers who are unfamiliar with chronographing .22LR ammo.
When making evaluations about any .22LR ammo chronograph results, it is very important to use as large a sample size as possible in order to get data that is more reliable. In other words, the smaller the sample size, the more unreliable the data. If going through the effort of using a chronograph it is far more useful to obtain the results of an entire box of ammo from a particular batch or lot than to shoot short strings of ten or 15 shots. That's more like seeing the entire movie rather than a few short snippets. Even half a movie is better than ten or fifteen minutes, although even that gives an incomplete picture.
What you should be looking for is what you can expect from a box of a certain batch of a particular brand of ammo. One of the most useful in particular is extreme spread found in a typical box of a certain ammo. This is increasingly important and useful as the shooting range increases. If shooting at 25 yards it won't matter a whit, but the further out you go the more the possible variation in MV between each round matters.
At the same time, it is important not to consider ES alone. It is possible that any box of ammo can have just a few outliers that produce a wide ES. The standard deviation (SD) figure is very important. The smaller the SD, the closer to the average MV the typical round in the batch will be. That is to say, if the ammo tested has a very small SD most of the rounds will have an MV very close to the average MV of the entire tested batch. The larger the SD, the more the MV of individual rounds will be to either end of the ES.
To illustrate with an example, consider two batches or lots of ammo. Both have the same average MV (or very close). They both have the same ES, say 100 fps. But both have different SD's. One is very low, the other much higher. The batch with the lower SD is much more desirable -- at least theoretically -- than the one with the high SD. Why? The individual rounds in the batch with the low SD will be close to the average MV, with a small number of outliers causing the high ES. In the batch with the high SD, the individual rounds will fall within the entire ES range, yet still have the same average MV. There will be many more rounds closer to the low and high ends of the muzzle velocity spread. Since it is preferable to have a batch of ammo in which individual rounds are close to each other in average MV, the lower the SD the better.
Of course it is not possible to determine what will in fact be the best ammo for accuracy in your particular rifle by using a chronograph alone. Sometimes even the ammo with the best chrony results will not be the best in accuracy results down range. But a chronograph can explain some of the results obtained, especially when shooting at longer ranges.
