I can vouch for Ironarm as well.
He's worked on both my M4 and M14.
M4: Replaced spring, cleaned, regreased, shimmed and corrected AoE
M14: All the above plus replaced Piston, Piston head, Spring guide, air nozzle... basically rebuilt the entire gearbox. He has experience with a ton of different gear boxes and guns.
The guy is top notch.
He keeps SoG up and running!