If you installed the Alpha Rail yourself, how did you do it? Did you partially tighten one clamp and then move to the next until all were tight? How did you ensure the rail is straight? What about the gap between the receiver and rail? Did you use loctite or rocksett on the screws?
I lined up the top of the rail with a tango down VFG to keep it straight and tight. The screw included blue lock tight so that is what i used. I slowly tighter the scrws in a star pattern about a half a turn each till all were the same torque (i don’t remember what torque i used but fairly tight). Then removed the VFG. No gap at the top and as lined up as it could possibly get. Hope this helps.
I use a one piece scope mount to bridge the receiver and handguard and check if the barrel is centered with a caliper by measuring the space between the OD of the barrel and ID of the handguard. Then I snug up the screws and give each an 1/8 or 1/4 turn until tight. It makes no difference to me if there’s a gap since the scope mount tells me the slots are correctly spaced.