Are you SURE you have the recoil spring in right?
It is a fairly easy thing to reverse the spring and that will cause all kinds of functioning problems.
Not with an EMP. The recoil spring and guide rod are an integrated unit and when you replace the recoil spring you buy a "kit" that is the recoil spring / guide rod as a single unit. The guide rod / spring "kit" can only be oriented one direction.
To the OP. I have used 124 grain Fiocchi ammunition in my EMP and it works reliably. Make sure you are using 124 grain ammunition or 147 grain ammunition until the pistol is broken in a bit. When new, you may find 115 grain ammunition does not cycle the gun properly. Make sure you have a good grip on the pistol and are holding your wrist relatively stiff against the recoil.