I have the PDF version of the manual, here is what it says...We have one at the range I work at and it only likes CCI Mini-Mag. I'm pretty sure it even says to run it in the owners manual.
I also found the following soon after I got mine...The .22 LR ammunition spectrum ranges from very light loads for single loader guns to sport load, utility load and on through to high speed
rounds. Unfortunately, however, it is not possible to adjust a semi-automatic gun to all loads. We have therefore decided to make an adjustment
to the loads that have priority for use with the MOSQUITO, which are the two major groups, utility and high-speed rounds. So to increase the round compatibility, we provide two slide springs for every pistol. The bigger bored version is designed for high-speed loads and is fitted in the pistol with delivery. The simple coiled smaller spring (marked white) is for standard loads and is supplied with the pistol.
Tip: It has been proven that many types of utility rounds function more smoothly if the rounds are lightly oiled.
I have found using Federal Auto Match (AM22) and CCI Mini-mags to be the most reliable ammo in the Mosquito. The Federal AM22 ammo needs less force to make it go boom. Anyone having light strike problems should try this ammo. Also placing a drop of oil in the hole on the side of the slide near the safety lever to lubricate the firing pin helps too. The Mosquito needs time to get broken in. These are the two types of ammo I recommend using at least for break in time. That could be as little as a couple hundred rounds or as much as 1,000. After that you might want to try some other ammo to see what works for you. I have found no difference in how the HP and solid Mini-mags function in this gun. You may find that one Mosquito will shoot better with a certain ammo and another one will do better with another. This is true for many rim fire guns. The AM22 and Mini-mags seem to cycle better then most. My Sport Model shoots the best with CCI Pistol Match or CCI SV. CCI Green Tag works about the same as the SV in these short barrels, but the cost difference is a lot. The AM22 are close behind. I do get some light loads with the AM22 that affect the accuracy. They seem to cycle fine and I have had very few duds. The duds are about 1 in every 15 boxes or so. It makes good plinking ammo.
When you are going to try different ammo I suggest using the drop test to see if it is going to give you problems prior to shooting it. The drop test is easy to do. First field strip your pistol. Point the barrel straight down then drop in the round you plan to use. If it seats all the way and tipping it up drops out it probably will work. If it doesn't drop all the way in or come out on its own weight you will probably have problems.