T77 Gas Problem?
 

Hi everyone, I'm new to the site and new to airsoft so bear with me. I have a HFC T77 all metal and what seems to be happening is the gas is released after 7-10 shots. The first few shots seem to go through fine but once I reach around 7 shots the power seems to decrease and the slide begins to close up. Once I reach around 10 shots bolt locks completely and it sounds like gas is released with a vibrating sound. Any ideas/solutions?