Upper Parts Kit

Kit Components

Standard Upper Parts Kit typically includes:

• Ejection port cover and spring
• Ejection port cover C-clip
• Forward assist assembly
• Forward assist spring
• Forward assist roll pin

Enhanced kits may also include:

• Barrel nut (specific to handguard system)
• Crush washer or shims
• Gas tube roll pin
• Handguard mounting hardware

Component Considerations

Forward Assist: The plunger assembly that allows manually pushing the BCG into battery. Quality forward assists have properly serrated faces and strong springs. Some builders omit this entirely (slick-side uppers) as it can force malfunctions worse if used incorrectly.

Ejection Port Cover: Keeps dust and debris out of the action. The spring should snap the cover open smartly when the BCG cycles. Quality covers have good finish and proper fit without being too tight.

Quality Indicators

Even these small parts benefit from quality manufacturing:

• Proper heat treatment on springs for longevity
• Good surface finish on the forward assist for smooth function
• Correct dimensions on the C-clip and pins
• Durable finish on the ejection port cover

When to Buy

If building from a stripped upper, you'll need these parts unless going slick-side. Many builders purchase complete upper parts kits from the same manufacturer as their upper receiver for consistent finish. If you're buying a complete upper or assembled stripped upper, these parts are typically already installed.

Slick-Side Alternative

If omitting the forward assist and ejection port cover for weight savings or aesthetics, ensure your stripped upper is designed as a slick-side (no forward assist bore or pivot holes). Converting a standard upper to slick-side requires plugging holes.