Would this be 2 heavy for gun sight installation or just what i need?

It might be to much for 271. It was designed for larger treads 3/8 + hold, and might make it impossible to remove at a latter time because of inability to apply enough heat and torque to remove from small treads like a scope mount. use Blue which is for small threads

Does this product require a primer? The fourth picture on Amazon suggests it does but the instructions do not mention a primer. Stainless + aluminum

I didn't need to. I used it on steel threads. Didn't even clean them. Applied this product and assembled. Hardened in minutes. I waiyed 24hrs before use just in case. Excellent product. I've used in the automobile repair industry for 30yrs.

Would this be appropriate for the locking nut on a sink faucet, that is always coming loose and making the faucet wobble?

Oh god no! This is for applications of extreme vibration and areas that's could be extremely dangerous if a bolt or nut came loose. All you should need for you faucet is the blue loctite. After using the red, you would need some serious heat and a breaker bar to free that nut if you needed to replace that faucet in the future.

if it is opened/used, how long will it stay fresh/usable?

Unopened/opened shelf life of Loctite 271 is two years from date of manufacture. Since exposure to oxygen is what keeps the liquid product stable, and it is packaged in a "breathable" plastic bottle, there is no change in shelf life once the product has been opened.

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Description

🔧 Lock it down like a pro — don’t let your bolts bail on you!

SHOCK VIBRATION PROOF - Engineered to secure components under extreme mechanical stress and harsh environments
QUICK SETTING CONVENIENCE - Starts curing in 10 minutes so your project moves fast without compromising strength
EASY DISASSEMBLY WITH HEAT - Strong hold that releases cleanly with localized heating and hand tools—no damage, no hassle
UNIVERSAL METAL COMPATIBILITY - Works flawlessly on stainless steel, aluminum, and plated surfaces—even oily ones
PROFESSIONAL GRADE RELIABILITY - Trusted by OEMs and pros for critical automotive and industrial use

LOCTITE 37421 Red Heavy Duty Threadlocker is a professional-grade adhesive designed for securing large bolts and studs (≥1 inch) in automotive and industrial settings. It bonds to all metals, tolerates minor oil contamination, sets quickly in 10 minutes, and fully cures in 24 hours. Resistant to shock, vibration, chemicals, and temperatures up to 140°F, it ensures durable, reliable fastening with easy heat-assisted disassembly.

Specifications

Brand	Loctite
Specific Uses For Product	Automotive, Industrial, DIY, Furniture, Heavy-Duty
Material	Metal-based formulation
Item Form	Tube
Special Feature	Strong
Colour	Red
Item Package Quantity	1
Package Information	Tube
Item Volume	6 Millilitres
Viscosity	Low viscosity
Full Cure Time	24 Hours
Water Resistance Level	Water Repellent
UPC	079340374218
Global Trade Identification Number	00079340374218
Manufacturer	Loctite
Model	LOCTITE 271 Threadlocker for Automotive \| Red, 6 ml Tube
Product Dimensions	16.51 x 9.69 x 2.03 cm; 4.54 g
Item model number	37421
Exterior	Packaged
Manufacturer Part Number	37421
OEM Part Number	37421
Stain Resistant?	Yes
Assembly Required	No
Special Features	Strong
Country of Origin	USA
Item Weight	4.54 g

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