I started using Loctite products over 45 years ago and I learned how well it performed while assembling aluminum parts for instrumentation. I now use it on my guns as I assemble them to prevent parts from coming loose from shock and vibration. I just put together a new AR15 build and I used it all over the gun for the accessory parts. I installed a new Magpul MIAD pistol grip, a Magpul vertical rail grip, a tactical flashlight, a Magpul front and rear MBUS set of sights, a Vortex 3X flip up scope and a Daniels Defense Omega Free floating hand guard quad rail. All of the screws and Allen head screws had Loctite applied as I did the assembly. I even applied it to the mounting screws on the Aimpoint Pro red dot sight.
I like the blue Loctite as it helps to hold the screws more securely in place and helps to prevent corrosion which is important on a rifle or gun. The blue formulation locks the parts in place but you can still take the gun apart when you need to. I recommend that you not use the red Loctite on gun assembly and it is very difficult to take apart as it has a much stronger holding power.
This is a great product with a proven history of working in difficult applications. I rated it at 5 stars and I recommend it to you.
Loctite Threadlocker 242 is an all-purpose, medium strength, blue threadlocker. Ideal for all nut and bolt applications 1⁄4" to 3⁄4" (6 mm to 19 mm). Eliminates the need for stocking expensive lock nuts and lock washers. Locks and seals while preventing parts from loosening due to vibration. Protects threads from corrosion. Removable with hand tools for easy disassembly. Typical Applications: Valve cover bolts, water pump bolts, oil pan bolts, drive shaft bolts, rocker arm adjustment nuts, carburetor studs.