5 Colt BCG Physicals

Published on April 29, 2020
Duration: 45:58

This video provides an in-depth physical inspection and gauging of five Colt Bolt Carrier Groups (BCGs) from various date ranges, including M16A1 kits, a Colt H-Bar Sporter, and a Colt Commando. The instructor meticulously examines each BCG for wear, corrosion, and dimensional accuracy using a variety of tools and gauges. The analysis covers critical components like the gas key, bolt tail, extractor, and firing pin, offering insights into the manufacturing tolerances and longevity of Colt BCGs across different generations.

Quick Summary

This video provides an in-depth physical inspection and gauging of five Colt Bolt Carrier Groups (BCGs) from various date ranges, including M16A1 kits, a Colt H-Bar Sporter, and a Colt Commando. The instructor meticulously examines each BCG for wear, corrosion, and dimensional accuracy using a variety of tools and gauges, offering insights into manufacturing tolerances and longevity.

Chapters

  1. 00:00Introduction to Colt BCGs
  2. 02:00M16A1 BCG Inspection
  3. 03:43Colt Markings and Gas Keys
  4. 04:12M16 Gas Tank Inspection
  5. 04:41Bolt Disassembly and Wear
  6. 07:53Bolt Tail Gauging
  7. 08:34Gas Key Gauging
  8. 08:55Magnetism Check
  9. 09:26Carrier Length Check
  10. 10:08Bolt Support Shoulder Diameter
  11. 11:04Cam Pin Fit in Bolt
  12. 11:28Firing Pin Protrusion Check
  13. 11:31Extractor Inspection
  14. 13:10Extractor Gauging
  15. 13:50Firing Pin Hole and Protrusion
  16. 14:28Carrier Key Obstruction Check
  17. 15:15Firing Pin Protrusion Measurement
  18. 16:02Firing Pin Gauge Explanation
  19. 17:30Headspace Check
  20. 18:38Carrier Key Screw Reverse Torque Test
  21. 20:09Sporter BCG Inspection
  22. 21:26Newer Colt BCGs with Dimples
  23. 22:31Gas Path and Bolt Tail Check
  24. 23:16Carrier Length Check (Newer BCGs)
  25. 24:02Extractor Gauging (Newer BCGs)
  26. 24:20Binding Check
  27. 24:34Gas Ring Test
  28. 25:12Extractor Check (Corrected)
  29. 25:34Overall BCG Face and Ejector Inspection
  30. 27:24Headspace Check (Newer BCGs)
  31. 28:06Bolt Shoulder Diameter (Newer BCGs)
  32. 28:22Protrusion Check (Commando BCG)
  33. 29:13Borescope Preparation
  34. 30:30Internal Inspection of M16A1 BCGs
  35. 30:42Bolt Support Shoulder Gauging (Newer BCGs)
  36. 32:24Gas Ring Run Gauging (Newer BCGs)
  37. 34:03Bolt Tail Gauging (Newer BCGs)
  38. 34:49Final BCG Gauging and Smell Check
  39. 35:47Straightness Test
  40. 37:14Borescope Inspection: Colt H-Bar Sporter
  41. 38:20Borescope Inspection: Colt Commando
  42. 40:10Borescope Inspection: M16A1 BCG 1
  43. 41:33Borescope Inspection: M16A1 BCG 2
  44. 42:41Borescope Inspection: M16A1 BCG 3
  45. 43:46Machining Quality Comparison
  46. 44:07Comparison: Colt 601/602 BCG Exterior
  47. 45:07Conclusion and Summary

Frequently Asked Questions

What are the key physical differences between older M16A1 Colt BCGs and newer Colt BCGs?

Older M16A1 Colt BCGs, particularly from the 1970s, often exhibit rougher machining on internal surfaces like the gas ring run and carrier opening. Newer Colt BCGs tend to have smoother finishes and may omit the 'C' marking found on older models. Both generations, however, generally maintain good functional dimensions and durability.

How does the instructor check for wear on a Colt Bolt Carrier Group?

The instructor uses a combination of visual inspection for hammer wear, lug wear, and erosion on the gas key. He also employs go/no-go gauges for bolt tail fit, checks for pitting and corrosion, and uses a borescope to examine internal surfaces for roughness and wear patterns. Firing pin protrusion and extractor claw condition are also assessed.

What is the significance of the extractor insert color on Colt M16 BCGs?

The color of the extractor insert on Colt M16 BCGs indicates the generation of the part. White inserts are typically found on first-generation M16s, red inserts on second and third generations, and later versions use black inserts with O-rings or black inserts with spring coils. This helps in identifying the age and potential compatibility of the BCG components.

Are Colt Bolt Carrier Groups prone to headspace issues?

Based on the testing of five Colt BCGs, headspace was not an issue. All bolts correctly closed on the GO gauge for 5.56mm but did not close on the FIELD gauge, indicating they were within proper headspace specifications. This suggests that Colt BCGs, even older ones, are generally manufactured to maintain correct headspace.

What are the common signs of wear on a Colt Bolt Carrier Group?

Common signs of wear include hammer wear on the carrier, wear on the lower lugs where they interact with the bolt, erosion on the gas key (more common in machine guns), pitting and corrosion on surfaces, rounded ejector edges, and wear on the bolt tail. The instructor also notes that aggressive cleaning can sometimes lead to visible marks or rougher surfaces.

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