Anyone has experience using real steel items on a AEG? I recently purchased a DPMS 7" Free Float Tube (Handguard) and was installing it on my G&P M4 (AEG) reciever yesterday. However it only screwed onto the reciever halfway before I couldn't screw it on anymore. Is this an Imperial/Metric threading issue? I always thought G&P used Imperial threading which is compatible with real steel parts. Or am I absolutely wrong on this? Thanks!