Bevel-to-Pinion Shimming

Shimming is one of the most heavily documented procedures in airsoft tech, and the existing material from the techs we trust is better than anything we would re-write. Rather than duplicate it, work from these references and apply the procedure with the Airsoft Mutation engraved shim set.

• The Real Deal Airsoft — full bench-side shimming walkthroughs on the gearset they manufacture.
• Paragon Armory — gear-train order (bevel → spur → sector) and AOE-aware shim sequencing.
• The Airsoft Tech — the underlying theory, including why the bevel is shimmed first against the pinion before anything else.

1. Bevel first. Shim until the bevel meshes correctly with the motor pinion at the height set by chapter 6. Close the shell with only the bevel installed and confirm zero axial play and zero scrape.
2. Spur second. Mesh against the bevel; adjust until full tooth engagement with no top- or bottom-of-tooth ride.
3. Sector last. Shim until the sector tooth face aligns with the piston rack plane.
4. Close the full train and spin the bevel by hand. All three gears must rotate as one smooth chain — no grind, no chirp, no axial wobble.

The Airsoft Mutation engraved set lets you nail each stack in two or three iterations rather than the guess-and-feel cycle that plain shim sets require.

A finished 6mmCustoms brushless SSG, shimmed correctly and with the gear axles polished per chapter 7, runs noticeably quieter than the same gearset shimmed without the axle polish. The gear noise floor drops to the point where the loudest sound in the cycle is the spring guide, not the gear train.