Hello, I currently own a Spikes Tactical ST15 Carbine and wanted to covert it into a midlength. I was going to replace the current gas tube with the Spikes Tactical MELONITED Midlength gas tube however it is out of stock. I found the WMD Nitromet gas tube and really just want to know the differences, pros/cons and what you would recommend. Also, I plan on moving the FSB forward and putting on a new mor handguard. Thank you.