FX400 Royal barrel inlet question

I have an FX400 Royal .177 and I shoot it SS. I also have the magazines for it but they won't slip into place. It appears that the barrel inlet (brass piece that the magazine slips onto) may be a bit too far into the breech area. Is the grub screw closest to the breech on the top of the receiver what holds the brass barrel inlet in place? If not how do I go about getting the barrel inlet adjusted? I just don't want to go turning things without knowing what I am affecting so thought I would ask and see what other Royale owners can tell me.

Thanks,
Brian
 
To property index the mag, loosen the 3 barrel set screw, cock and place safety on try inserting the mag in the breech, if barrel is in the way move barrel forward till mag slip into place now lightly move barrel back till lightly thuching the mag, remove and reinstall mag 3 time this will allow proper clearance. Remove one barrel set screw and look for proper alignment for set screw to barrel debit marking, rotate barrel left or right for proper alignments if needed then bouble check mag for proper clearance before tightening the barrel set screw.

Ernest