Understanding BCG Performance: TruPrep’s Gauging Results and Service

At TruPrep, we’re committed to ensuring your AR runs reliably. A critical component in this is the Bolt Carrier Group (BCG), the heart of the AR’s Cycle of Operations. Our expert armorer, Rob Sheppard, gauges BCGs to assess their gas-handling efficiency, and we’re sharing insights from our ongoing testing.

The Role of the BCG

The BCG is the only AR component involved in all eight stages of the Cycle of Operations: Firing, Unlocking, Extracting, Ejecting, Cocking, Feeding, Chambering, and Locking. Efficient gas management by the BCG ensures reliability and minimizes recoil. Using precision gauges, we measure critical dimensions to evaluate performance.

Gauging Process and Color Coding

We assess key BCG areas: Primary Bore, Secondary Bore, Tertiary Bore, Bolt Tail, Gas Key Bore, Key Alignment, and Extractor. Our color-coded system indicates performance:

• Green (G, G1, G2): Optimal gas handling. G1 is tighter than G2.
• Yellow (Y, Y1, Y2): Inefficient gas handling. Y2 is less efficient than Y1.
• Red (R, R1, R2): Failure in gas handling. R2 is worse than R1.
• X: Not tested or applicable.

Key areas measured include:

• Primary Bore: First bolt entry point.
• Secondary Bore: Where gas rings compress and seal.
• Tertiary Bore: Bolt tail passage.
• Gas Key Bore: Gas tube entry point.
• Key Alignment: Gas key centering with the receiver’s gas tube hole.
• Extractor: Extractor groove performance.
  
  

Key Findings from Our Data

Our growing dataset reveals trends across brands and finishes:

• High Performers: Brands like Centurion Arms, Microbest, and SOLGW frequently score Green across most measurements, indicating reliable gas handling, especially in new manganese phosphate BCGs.
• Common Issues: FailZero and Aero Precision BCGs often show Yellow or Red in Primary and Secondary Bores, suggesting inefficiencies, particularly in used or nitride-coated units.
• Notable Failures: Some BCGs, like those from PSA and FoldAR, scored Red in multiple areas, indicating poor gas handling. One BCA side-charging BCG had a broken gas key.
• Finish Impact: Manganese phosphate and hard chrome finishes generally perform better than nitride or NiB, though exceptions exist (e.g., Wilson Combat’s NiB failed the gas ring test).
• Interesting note: A Young Mfg BCG lacked forward assist serrations, which may affect compatibility in some setups.

Why Gauge Your BCG?

Gauging identifies inefficiencies that could cause malfunctions or excessive recoil. For just $25, TruPrep offers this service in minutes, provided your BCG is moderately clean (cleaning incurs extra cost). Our armorer’s expertise ensures your AR performs at its best.

Schedule Your BCG Gauging

Visit TruPrep to have your BCG gauged by Shep. Ensure your firearm’s reliability with our precision service.  Also be sure to check out the rest of our Armorer Services.  Contact us to learn more or see our testing in action!

Testing Results