i am at about 650 rounds in to a pt1911 that was bought new. i am using chip mccormick power mags. when i am 8 in the mag and one in the chamber the trigger pull feels almost double what it is on the rest of the shots. my friend thinks it may be the power mags however this just started the past couple of days. if i load 7 in the mag and 1 in the chamber it's fine. any ideas as to what this is???