Wildcat 22 pellet trials

have been working with my 22 wildcat trying different pellets. So far only tried JSB and have not run a crony on it yet. Started shooting at 50 yards shooting splatter burst 2 in targets with 1/2 inch centers. Have been filling to 220 bar and shooting 5 magazines before refill. Shooting 8 round groups. Wind has been calm. 14.35 grain were all over the place. Lucky to keep them in the 2 in target. The 15.89 grain are just amazing. Not only do they stay within the 1/2 in target centers, but I can place the shot within-in the center. The 18.13 grain are almost as accurate as the 15.89, but not quite. The 25.39 grain monsters are a wonderment. At 50 yards they are lucky to stay within a 2 ft circle and the direction is random. Couldn't figure out where the first three shots even went. So far with the 15.89 gr this gun is the most accurate air gun I have ever shot. Could not be happier. It is also the smoothest I have ever run. The one qurk I have observed is with the 14.35 gr pellet on occasion it will eject the magazine. When it does there will be a bent skirt on one of the pellets and it will be backed out of the magazine. Go figure. The gun doesn't like the 14.35 gr so that problem is solved. This will be one of those guns I will keep forever. So far I've shot about 2000 rounds. Just my observation. 
 
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Thanks all for your answers and links, I see several different variations in sizes (5.51mm, 5.52mm) of 15.89 JSBs in local shops where I live, so wanted to check which ones exactly were used. None of them seems to be identical to those pictured on AOA and pyramydair, judging by the images of their boxes. Might be as well the same just different batches, o simply webmasters of eshops are too lazy to update images :) Think i am gonna pay them a visit as the shop is located just accross the street from my office. Thanks again!