In rifle and pistol shooting, the result depends not only on you and your weapon but also on the ammunition. Air weapons use pellets, and smallbore weapons use .22 LR (5.6 mm) rimfire cartridges.
Air weapon pellets
Air pellets are lead or lead-alloy wadcutters with a wide head and a skirt. Sport air weapons use 4.5 mm caliber. The skirt expands under air pressure and seals the barrel.
The main parameters are caliber, weight, and head size. A weapon may shoot one brand better than another even when the caliber matches. So you match pellets to a specific barrel, not to the price.
Do not mix lots
Pellets from different tins and lots can differ in head size. Use pellets from one lot for competition and for zeroing.
Smallbore cartridges
.22 LR cartridges come in several grades, from training to match. Match cartridges are made to tighter tolerances on bullet weight and charge, so they show less velocity spread and better grouping.
Training cartridges work for practicing position and trigger control, where top accuracy is not needed. At important matches, shooters usually use match cartridges.
Choosing a lot
Even within one brand, cartridges from different lots behave differently. That is why shooters choose a lot: test several and keep the one that groups best from your weapon.
To test, shoot groups from a rest, one brand at a time, and compare grouping and MPI. One group is not enough. You need several to separate lot spread from your own spread. When you find a good lot, buy enough for the season so you do not have to zero again.
After you change lots, check your zeroing again.
Handling and storage
Safety
Keep cartridges and pellets apart from the weapon, in a dry place, out of reach of children. Do not use damaged, rusty, or deformed cartridges.
Buying, transporting, and storing ammunition is governed by the laws of your country. Follow them and ask your club or coach about local rules. For practical advice, see storage.