I just recently purchased a PDI hard piston and a PDI steel spring guide for my UTG Mk96. You can immagine my dissapointment when they were both too wide for the cylender. So naturally, i have a few questions. Is this typical of upgrades not fitting the stock parts? Is there anything I can do to alter it? and lastly (and most embarissingly) before I spend any more money, this IS an APS2 rifle correct???