hey dont buy barrel remove you moderator and shoot a few groups , and post them with and with out moderator , If you say crown is good , I assume you mean you put it on a lathe and barrel is square and straight ? hey shoot groups if you think it is barrel , I can put it on my lathe and spin it by eye a bad crown is almost impossible to see . but hatsan sells barrels
I have had square shrouds on my hatsan btg5 and it was all over as it clipped moderator ,
secondly polishing barrel wont boost power , if you want to boost power you need to change hst or weight or port sizes , as far as some shoot hi and some low sounds like you clipping