On another related note extending from my previous comments, experienced shooters are aware of the following, but it's worth repeating for those who are less familiar with .22LR ammunition.
There are many variables when it comes to consistent shooting ammo. Ammo has variation in bullet diameter, rim thickness, overall length, lubrication, and component weights, including casing, powder, and bullet. Variation can also occur in other more difficult to measure areas including primer compound and distribution, case thickness consistency, bullet composition, and powder consistency to name a few.
It may not be only a certain average MV that determines the most consistent results, although in theory if not in practice it certainly helps to have ammo with a low ES and as low an SD as possible. MV's that are printed on a box as it is with Eley or determined by a formula involving the lot number as is said to be the case with Lapua are the average MV recorded with the manufacturer's test rifles. These figures don't reveal any information about ES or SD.
In fact SD may be even more important than ES. Standard deviation indicates how close to the average MV the majority of the ammo in question actually is. An ES of 40 fps is not bad in itself, but if the majority of individual rounds have an actual MV closer to both the high end and the low end of the ES then that ammo is less desirable than a batch of ammo that has most of the individual rounds much closer to the average MV but with a few outliers producing the ES figure.
In short, the lower the SD the better. Unfortunately, shooters can't know the SD until it has been calculated after chronographing the ammo. An exceptionally low SD for .22LR ammo would be around 5 but figures between 10 and 15 can still be useful for target ammo. Higher SD's are not uncommon with many makes of ammo, even with match ammos.
To illustrate standard deviation, an SD of 10 means that two-thirds (roughly 68%) of the ammo in that particular batch will shoot within 10 fps (plus or minus) of the average muzzle velocity. That means an ES for that ammo of 20 fps for that two-thirds of the ammo. The remaining third, that is every one out of three rounds, will have an even higher or lower MV.
Below is a diagram with a more detailed explanation. Consider .22LR standard velocity MV's rather than those offered here and the results are still the same.
As noted above, it is not possible to know without the use of a chronograph what the SD of any particular ammo is.
Adding to the complexity is that rifle barrels are not all the same either. Barrels vary in length and diameter. Some are longer and some are heavier. The barrel bores themselves, like bullets, can vary in internal diameter from one make to another, indeed even between rifles of the same model. Bores are not always perfectly straight and their alignment can affect results. Barrel metallurgy is not necessarily the same from one rifle to another. On the inside the rifling can differ between manufacturers and individual rifles, and not only in the number or shape of the lands and grooves. Some bores are more worn than others, more smooth or more rough.
The result is that two rifles, even of the same make and model, may shoot the same ammo differently. The average MV for a particular ammo can change from one rifle to another and so, too, can the SD.
The variation in individual bullets and individual barrels/bores result in a interaction between the two that can be difficult to predict without the practical experience of shooting the ammo with the rifle in question and seeing the results over a good sample size.
This is why it is so important to find the lot(s) that best suit a particular rifle and the conditions under which it is used. To be sure an average lot should produce average results most of the time. But it can be disappointing to have a poorly shooting lot of what is often expensive ammo. At the same time, when a good lot is in hand the results can be most gratifying.
