Can you take some picture of your nozzle, I will compare with mine. (I only need the right side where's your nozzle, don't remove all parts)
If you have any warranty beware but if not, you can remove each part of you easly
BROKEN! Magpul Masada/ACR PTS Airsoft Version Repair Video PART 1 - YouTube
(don't listen too much how he doesn't like his masada, the guy modified too much the gearbox and he exploded it during a game...)
If your trouble is due to the nozzle or the hop up, I found this ( never tryed but installation at
http://www.wiitech.com.hk/eshop/prod...roducts_id=331 )
http://www.ebay.ca/itm/WII-TECH-Masa...item3cbe9b2c29
You can check with spartan for the original part ( and ask to your retailer, for a new part, check explode view for the part number )