You beat me to it NHT3. If you used blue and it didn't work, the threads may have had a bit of oil on them. Clean the male and female threads with solvent and put a drop of loctite on the screw threads. Loctite primer is not required but sets up quickly and has a higher shear strength. Great products.I believe the prep is the most important part. Making sure the parts are clean and using loctite primer should assure success..
[FONT="]NRA Life member [/FONT][FONT="]GSSF member[/FONT][FONT="]
Gunsite graduate Certified Glock armorer[/FONT]
Loc-tite red is,"stud and bearing locker", and is generally for parts like cylinder head studs that you never intend to remove. The blue is,"thread locker", and is what I use for gun parts. I spent thirty years in aviation and also operated my own racing team for awhile. We never used the red on anything that we even remotely thought we might need to adjust or remove later as it does require a lot of heat and or elbow grease to remove. (Usually destroys the head on the fastener during removal too).