Bernard 4478 Replacement O-Ring for 400A MIG Guns

Stop Leaks with the Bernard 4478 O-Ring

Is your MIG gun sputtering or losing gas coverage? A worn-out O-ring could be the culprit. The Bernard 4478 O-Ring is the direct replacement seal you need to get your 400 Amp Bernard MIG gun back in top fighting shape. Located typically at connection points like the gun neck or power pin, this O-ring creates the airtight seal necessary for shielding gas to reach the weld pool without contamination.

Don't let a ten-cent part ruin a thousand-dollar weld. Over time, heat and mechanical stress cause rubber seals to dry out, crack, or flatten. Replacing your O-rings during liner changes or deep cleans is a smart habit for any professional welder. This specific 4478 model is built to handle the heat and pressure associated with 400A welding applications, providing a long-lasting seal that resists hardening better than generic alternatives.

Key Benefits:

• Perfect Fit: Designed by Bernard for Bernard guns—no forcing or guessing.
• Leak Prevention: Stops shielding gas loss, saving money and improving weld appearance.
• Easy Installation: Swaps out in seconds during routine maintenance.

Keep a few of these in your toolbox so you're never stuck waiting on parts when a seal fails in the middle of a job. A tight seal means better welds and less porosity.