I've got a UMP that shoots great unsuppressed, but when I throw on the AAC Evo-45, I'm shooting 6 inches low at 25 yards. I'm pretty sure this is not normal. WWB is type of ammo. Shift is repeatable, but 6 inches? My Evo-9 shift is only an inch. Cyclone has almost no shift. I had a reputable smith thread the barrel. The sound suppression is great, but the shift is killing me, especially with open sights. Anything I can do, any ideas?