hi countryman
i have owned a AATX200HC .22 and had good results with it!,are you on about the plenum insert? the pointed pellets arent the best out to 30yds,try aa domed 4.52
if so ditch that and get your self a screw on moderator,aafield are one of the best brands on the market,but this depends on your barrel as every one is different.it also may be cliping the insert,remove it and try its grouping,because these are defo good rifles
is it new? if so it may take a 1000 pellets to bed in!
or second hand? ask the previous owner what they were using!
if the problem continues then post