Today I was at a skirmish down in croydon and I was experiencing issues with my buffer tube. It was already a bit wobbly to begin with so I made sure to tighten the screw but it just kept giving out on me in the middle of games and was falling off (the screw only held in the bottom part and the top was still wobbling even though the screw was tightened very well). The 4th time it fell off I lost the screw and was left with no choice but to return home since it was impossible to play with anymore. Its an ICS CXP 16. Could someone let me know what I need to purchase to fix it?