Picked up a new never used G27 which was orig mfg for PD use. Came with two 9 round mags featuring the finger grip. Picked up a Glock 9 round flat base mag and when loaded with 9 rounds I cannot get the slide to cycle????? Does this possibly have something to do with it being a PD mfg gun? The two that came with the gun have noted on the mag "for PD and Govt use only". Any ideas?