Hoppe's No. 9 Gun Bore Cleaner

Hoppe's No. 9 has been the default gun cleaning solvent in the United States since 1903, and that longevity is not an accident. The petroleum-based formula combines an aggressive blend of hydrocarbons and ammonia-derived compounds that dissolve carbon fouling, burnt powder residue, and lead deposits from bore surfaces. The ammonia content provides secondary copper-fouling removal capability, though dedicated copper solvents will strip heavy jacket deposits faster. For routine post-range cleaning of .223/5.56 bores, No. 9 handles the job in a single soaking cycle.

The solvent works by penetrating the microscopic pores of barrel steel, lifting embedded fouling that patches alone cannot reach. Apply a saturated patch, let it soak for 10-15 minutes, follow with a bore brush, then run dry patches until they come out clean. On heavily fouled bores, a second soak cycle may be necessary. The formula is safe on blued, parkerized, and stainless steel finishes but should be kept away from wood stocks and polymer components, as the petroleum base can soften or discolor these materials over extended contact.

The tradeoff for this effectiveness is the distinctive, strong odor that defines the product. This is not an indoor-friendly cleaner unless you have dedicated ventilation. Basements, apartments, and enclosed workshops will hold the smell for hours. For shooters who clean indoors, odorless alternatives like Breakthrough Clean are a better choice. But for outdoor cleaning stations, garage workbenches with an open door, or anyone who grew up associating that smell with a day at the range, Hoppe's No. 9 remains the benchmark solvent that every alternative is measured against.