Loctite 243 Blue Threadlocker

Loctite 243 Blue Threadlocker serves as the firearms industry standard for securing threaded fasteners that require future removal capability. This medium-strength anaerobic adhesive cures in the absence of air between close-fitting metal surfaces, creating a robust bond that prevents vibration-induced loosening while remaining removable with standard hand tools. The blue color provides visual confirmation of application, making it easy to verify which fasteners have been secured during assembly or maintenance operations.

The 243 formulation represents an improved version of the classic 242, specifically engineered with enhanced oil tolerance that makes it ideal for firearm applications where residual lubricants and cleaning solvents are common. This primerless design works on all metals including passive substrates such as stainless steel, aluminum, and plated surfaces without requiring additional surface preparation. The threadlocker has been proven tolerant of minor contamination from industrial oils, motor oils, corrosion prevention oils, and cutting fluids, allowing reliable bonding even on parts that haven't been thoroughly degreased.

Performance specifications include 1,100 psi compressive shear strength, with Henkel listing breakaway torque around 230 in-lb and prevail torque around 40 in-lb on M10 steel nuts and bolts. The operating temperature range spans -65°F to +360°F, covering all normal firearms use conditions from winter hunting to suppressed rapid fire. The 24-hour cure time allows for adjustment during initial installation, with handling strength developing within a few hours. Common applications include scope ring screws, optic mount bolts, rail mounting screws, handguard mounting hardware, and any fastener subject to recoil vibration that may need periodic removal for maintenance or upgrades.