Nice, could use some improvements
The first thing I'd change is the synth pad in the background- after a while of listening to that one chord, I have the slight feeling I might get a headache. Some flanger or phaser (slow frequency) might do the trick, as well as some panning-alteration. The riffs were nice, and yes, they were kinda Maiden-ey, I have to admit, but I liked them. The sound of the bass was cool, really thick 'n' juicy, the guitar was ok (which is the most a person can expect from synth guitars, sadly), and the drums were cool, especially the snare.
The change of pace in the mid of the song was a good choice, keeping it at the same beat from top to bottom would kill the song. As for the sound effects in that section, some panning might have done wonders here, too. The gunshot was ok, the last part too, but that machinegun was just a tad too bland without any volume and pan differences.
Also, you might want to consider reducing the volume of each instrument individually: this loudness creates a bit too much static at certain points of the song. Plus, the end-explosion (though serving a shock-factor of sorts) is still way too loud in comparison to the other instruments. Aim for "louder than the rest", not "as loud as it goes". Modify these things, and you've got a really nice piece here!