Air compressors

Nail gun misfiring or double-firing

Misfires and unwanted double-fires usually come from a worn or dirty trigger valve, bounce-fire mode being used incorrectly, or excess air pressure. Most cases are solved with cleaning and correct pressure, but a worn trigger valve needs replacement.

Difficulty
Moderate
Time
10–30 minutes
DIY cost
$5–$20
Pro cost
$40–$90

Symptoms

  • Gun fires two nails per pull
  • Gun fires when just bumped, not intentionally
  • Delayed or hesitant firing
  • Gun fires without full contact with the work surface

Likely causes

  • CommonGun set to bump-fire (contact) modeBump-fire mode fires every time the tip contacts a surface with the trigger held, which feels like double-firing if you're not used to it.
  • CommonAir pressure set too highExcess PSI beyond the gun's rated range can cause erratic cycling.
  • PossibleWorn or gummed trigger valve or safety tipBuildup or wear here can make the valve stick partly open.
  • PossibleWorn O-rings in the firing valveLeads to inconsistent air release and double cycling.
  • Less commonDry firing (no lubrication) on oil-requiring gunsSome pneumatic nailers need daily oiling; without it, internal parts stick and misfire.

What to do

  1. Disconnect the air hose and check the gun's mode selector; switch to sequential (single-fire) mode if bump-firing wasn't intended.
  2. Check your compressor's output pressure against the nail gun's rated PSI range and turn the regulator down if it's too high.
  3. If the gun requires oil, add a few drops of pneumatic tool oil into the air inlet as the manual specifies.
  4. Reconnect air and test on scrap wood, watching whether the tip safety mechanism moves freely.
  5. Clean the safety tip and trigger area with compressed air if it feels sticky or sluggish.
  6. If double-firing continues in sequential mode at correct pressure, the trigger valve or O-rings are likely worn and need replacement.
  7. Stop use and have it serviced rather than continuing to use a gun that fires unpredictably.

Tools and parts

  • Pneumatic tool oil
  • Compressed air/blower
Nail gun O-ring rebuild kitSearch: “nail gun trigger valve O-ring kit”
Pneumatic tool oilSearch: “air tool oil”

When to call a pro

If double-firing continues after a mode check and cleaning, a tool repair shop can replace the trigger valve assembly.

Safety

Use caution

A gun that fires unpredictably is a safety hazard; stop using it until fixed and always keep it pointed away from people.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.