Chapter 13 of 13
Final Testing & QA
Break-in sequence, QA checklist, and the symptom-to-cause table for the most common brushless SSG failures.
10 min
- Step 1
Break-in sequence
First 500 rounds, in this order:
- Cycle 50 rounds dry-fired through the chrono. Document FPS every 10 shots. Variance should fall inside ±3 FPS by shot 50. If it doesn't, re-leak-test the compression chain (chapter 5).
- Cycle 100 rounds on semi at 1 round/sec. Verify trigger response is consistent shot-to-shot. Any drag means the pre-cock hold is too long; reduce in 50 ms steps.
- Cycle 200 rounds on semi at 3 rounds/sec. Verify the motor stays cool to the touch and the gearbox stays under 100°F. Any heat above ambient + 30°F means pinion mesh is wrong or AOE is off.
- Cycle 150 rounds in 30-round bursts on auto. Verify ROF is within ±1 RPS of the 30 RPS cap. Listen for piston slap — there should be none.
- Step 2
QA checklist before handover
- Compression: 28+ mL hold over 1 second on the syringe test, re-verified after break-in
- Pinion mesh: clean wear band centered on the bevel after 500 rounds
- AOE: piston rack inspection through the cylinder window shows no first-tooth deformation
- Chrono: ±3 FPS over 50 shots, 0.20g, average documented
- ROF: within 1 RPS of the 30 RPS cap, 11.1V LiPo, 0.28g
- Trigger: < 30 ms shot-to-shot, semi, pre-cock confirmed
- Wiring: no exposed strands, no kinks, no insulation cracks at the trigger guard radius
- Build certificate: full parts list, MOSFET profile, chrono and ROF results
- Step 3
Symptom → cause table
Symptom Most likely cause Verification Fix Motor spools, gears don't move Reversed phase wires Swap any two phase leads at the ESC pigtail Re-solder correct phase order Trigger pull → dead click, then fires on second pull Pre-cock dropping out from battery sag Voltmeter under load shows < 10.5V at battery Replace battery with fresh 30C+ 1500 mAh FPS drops 30+ from baseline after 1000 rounds Cylinder head O-ring extruded under cycle pressure Pull cylinder, inspect O-ring groove Replace O-ring; re-seat dry Audible piston slap on every shot AOE skew, sector engaging rack at < 85° Re-open shell, inspect first sector tooth contact Add an AOE washer (or remove one), retest Sharp metallic chirp on startup Pinion sitting too high on bevel Pull motor, inspect bevel face for top-of-tooth wear band Snug motor screws, re-shim bevel down ROF erratic between shots Active brake disabled or set partial Pull MOSFET via app/USB, read profile Re-enable active brake at full Trigger contact "stuck" Optical sensor fouled with grease Inspect MOSFET optical window Clean with IPA on a swab; never grease the optical sensor Sudden ESC fault, no motor response LiPo over-discharge under LVC Read LVC log on the MOSFET Replace LiPo, verify LVC at 9.6V - Step 4
Documentation
Hand the customer:
- Build certificate (parts, MOSFET profile, chrono, ROF)
- Re-order links for every consumable (spring, bucking, nub, piston O-ring)
- Service interval reminder (re-shim and re-leak-test at 25,000 rounds)
End of build.