To clean an optic, blow or brush the grit off first, then wipe the lens gently with lens fluid and a clean microfibre cloth. Never dry-wipe it with your shirt. To maintain a weapon light, keep the battery contacts and tailcap threads clean, replace all its cells together, and take the batteries out of anything going into storage. Add a periodic check of mount screws and zero, and most "failures" never happen.
Almost none of this takes more than a few minutes. Doing it wrong, especially on coated glass, can cause damage that no amount of care will undo. Here is the routine we'd follow.
Key takeaways
- Remove loose grit before anything touches the glass; dragging grit across a lens is what scratches coatings.
- Dirty contacts and part-flat cells are the commonest causes of a light or dot that "died" in the field.
- Replace all the batteries in a multi-cell light at the same time, as SureFire's battery guidance instructs.
- Recheck mount screws and zero after heavy sessions, but never apply thread-locker near adjustment turrets.
- Store optics and lights cool and dry, with batteries removed for long-term storage.
Cleaning lenses without scratching them
Lens coatings are thin, hard layers, and grit is harder still. The order of operations matters more than the product you use.
- Blow or brush off loose grit with a hand blower or soft lens brush. This is the step that prevents scratches.
- Loosen what's left with a purpose-made lens fluid, or by breathing lightly on the glass.
- Wipe gently with a clean microfibre cloth or lens tissue, working in small circles from the centre outwards. Change to a clean part of the cloth as you go.
- For stubborn marks, use a lens pen or a wipe made for optical coatings. Avoid household glass cleaners, kitchen roll and your shirt tail.
On a red dot, clean both sides of the window. The inner face picks up powder residue and fingerprints too, and a smear there makes the dot flare. If you shoot with astigmatism and the dot still looks like a starburst on clean glass, the cause is probably astigmatism in your eye rather than the lens.
Battery care for optics and lights
Batteries cause more apparent failures than anything else.
- Change on a schedule, not when the dot dies. Write the date on a small label in the case, or change them at the start of each season.
- Replace all cells together. In a two-cell light, a fresh cell paired with a part-used one gets dragged down by it. SureFire's battery-safety guidance says to replace all batteries at the same time (SureFire battery safety).
- Use the cells the manufacturer specifies. SureFire warns that counterfeit and inferior lithium cells have caused fires. It also says that the only rechargeable cells to use in its LED lights designed for 123A primaries are its own LFP 123A rechargeables.
- Take batteries out of anything going into long-term storage. That protects the contacts if a cell fails.
- Carry a spare. Most red dots use a CR2032 and most weapon lights a CR123A or a rechargeable pack; check yours against our red dot battery chart.
Rechargeable lights need a different habit: top them up before you go out rather than trusting last month's charge. The trade-offs between cell types are covered in rechargeable vs CR123.
Contacts, threads and switches on weapon lights
- Clean the contacts. Use a cotton bud with a little isopropyl alcohol on the battery contacts, the tailcap spring and the end of the body tube. Let it dry before reassembling.
- Keep threads clean. Grit in tailcap threads can stop the cap seating fully, which gives you a light that flickers or fails under recoil.
- Look after the O-rings. Check them for nicks, and use only the grease the manufacturer recommends, applied sparingly. A dry or damaged O-ring is how water gets in.
- Inspect remote cables. Pressure-pad cables get snagged and pinched. Route them along the handguard, and replace a switch whose cable is kinked or cut. SureFire tailcaps and remotes are sold separately in weapon light accessories.
Check torque and zero
Recoil and handling slowly loosen fasteners. After a heavy session, and at least once a season, check mount screws with an inch-pound torque driver set to the figure in the mount maker's instructions, then confirm your zero on paper. A small amount of removable (medium-strength) thread-locker on base screws helps. Keep it well away from turret mechanisms and anything designed to move.
If a screw head is chewed or a mount has been refitted too many times, replace it rather than persevere. For red dots we carry Trijicon's RMR Picatinny and ACOG adapter mounts in red dot sight mounts. We don't currently stock scope rings or cantilever scope mounts.
Body, seals and storage
Wipe optic and light bodies with a slightly damp cloth and dry them fully. Keep solvents off rubber armour and seals. After a wet day, let everything dry at room temperature with the caps off before it goes back in a closed case. Sealing damp kit into a case is how condensation and, eventually, fungus on glass start.
Store kit somewhere cool and dry, put a silica-gel sachet in the case, and fit lens covers. Don't leave optics baking in a car in summer. If you shoot in constant rain, mud or dust, an enclosed-emitter red dot has less to go wrong in the first place; enclosed vs open red dots explains why. What waterproof ratings actually promise is set out in IP ratings explained.
Expert tip
When a light flickers, work from the back forwards. First reseat the tailcap, then clean the contacts, then fit fresh cells, and only then suspect the switch or the head. More often than not the fault is in the first two steps, and those cost nothing to fix.
A simple routine
| When | Optic | Weapon light |
|---|---|---|
| After each outing | Blow off grit, wipe body, check lenses | Wipe body and lens, check tailcap is tight |
| Monthly or seasonally | Check mount torque and zero, inspect battery contacts | Clean contacts and threads, check O-rings and remote cable |
| Start of season | Fresh battery, confirm zero | Fresh cells or full charge, function check on every mode |
| Long-term storage | Remove battery, add silica gel, fit covers | Remove cells, store dry |
Frequently asked questions
Can I clean a scope lens with my shirt?
No. Fabric drags grit across the coating, and that is how permanent scratches happen. Blow the grit off first, then use lens fluid and a clean microfibre cloth.
How often should I change a red dot battery?
On a schedule, typically once a year or at the start of each season, whatever the rated battery life says. It costs very little and prevents a dead dot on the day.
Why does my weapon light flicker?
Usually a loose tailcap, dirty contacts or a tired cell. Clean the contacts and threads and fit fresh batteries before you suspect the switch.
Should I use thread-locker on optic mounts?
A small amount of removable thread-locker on base screws is common practice. Follow the mount maker's instructions, and never use it on turrets or adjustment mechanisms.
Shop this guide
- Weapon light accessories: replacement tailcaps and remote switches.
- Rechargeable weapon lights: if you are getting through primaries.
- Enclosed red dot sights: sealed emitters for wet, dirty conditions.
- Red dot sight mounts: Trijicon mounting options.
