I was thinking of the following method for choosing the right pellets for a particular rifle:
Get a chrony and different brands/shape pellets. First put the chrony 30cm from the rifle and start shooting 10 pellets of the same brand/shape. Change the brand/shape of pellets with another and shoot 10 again. After you try several types of pellets this should give you indication if the rifle doesn't like the pellets due to their size or if the spring is inconsistent. However while loading of you notice a for a particular type of pellets some of the pellets to fit tighter, some looser in the barrel, just throw them away and ignore the results from them, unless you want to spend the time of sorting those by size and weight.
Then put the chrony 10m away from the rifle and start shooting 5-10 shots with one type of pellets. Move the chrony to 20m and repeat the shooting. Keep on increasing the distance between the rifle and the chrony by 10m to whatever distance you thing you can hit consistently. Then change the pellets type and start again from 10m upwards.
During this you don't even have to aim at a target, just make sure the pellets go through the chrony.
After that choose may be 3-5 types of pellets with least deviation at each distance, put the rifle on a bench and start shooting groups with one of those types by increasing the distance again with 10m after 5-10 shots. Change the type and test groupings again at different ranges.
The above tests should be able to determine the best ballistic characteristics to match rifle/pellets/distance and I donít think itíll take longer than a lazy afternoon.
From then on you just have to work on your shooting technique with the best matches.
Am I missing something?