The ORIGINAL Colt M5 and SCW Stock Development

Published on March 16, 2026
Duration: 33:55

This video delves into the development of Colt's early external piston rifles, specifically the M5 and LE 1020. It highlights the design philosophies of engineers like Greg Grechenko, the technical differences between the M5 and LE 1020, and the reasons behind the M5's cancellation. The SCW stock development is also explored as a separate but related project by Grechenko.

Quick Summary

The Colt M5 was an experimental external piston rifle developed around 2006-2007, featuring a 5.56x45mm caliber and a unique heat evacuation system. Designed by Greg Grechenko, it drew inspiration from AK-47 piston systems and utilized a standard M4 upper receiver. Despite extensive testing, the M5 was canceled in favor of the more mature LE 1020 design.

Chapters

  1. 00:00:08Introduction to the Colt M5
  2. 00:00:14M5 vs. Current M5 Distinction
  3. 00:00:23Colt's Response to External Piston Trend
  4. 00:01:13SCAR Type-C and LE 1020 Precursors
  5. 00:01:37M5 Specifications Overview
  6. 00:02:14M5 Markings and Designer (Grechenko)
  7. 00:03:02Colt's Two-Team Development Strategy
  8. 00:03:19The LE 1020 Design and Team
  9. 00:04:07The M5 Design by Greg Grechenko
  10. 00:04:40M5 Piston System Patents
  11. 00:05:07M5 vs. LE 1020 Receiver Differences
  12. 00:06:47M5 Front Sight Base Variations
  13. 00:08:29Gas System Differences: M5 vs. LE 1020
  14. 00:09:05M5 Gas System Evolution
  15. 00:09:38Cutaway of the M5 Gas System
  16. 00:10:19M5 Cycle of Operations
  17. 00:11:21M5 Disassembly and Handguard
  18. 00:12:24Close-up of M5 Gas System Components
  19. 00:13:09M5 Heat Evacuation System
  20. 00:13:38M5 Barrel Fluting and Heat Pump Effect
  21. 00:14:35M5 Heat Sink System Details
  22. 00:15:23M5 Front Sight Base (AK Profile)
  23. 00:15:43M5 Bolt Carrier and Carrier Key Design
  24. 00:16:49M5 Testing Data (18,000+ Rounds)
  25. 00:17:26M5 Water Immersion Test
  26. 00:18:44Impact of Two-Team Strategy
  27. 00:19:08Colt Chooses LE 1020 Over M5
  28. 00:19:55Expert Opinion on M5 and LE 1020
  29. 00:21:18Reviewer's Impressions of the M5
  30. 00:22:02M5 Carrier Tilt Issue
  31. 00:23:03M5 Obscurity and Colt's Secrecy
  32. 00:24:25Colt's Late Entry into Piston Market
  33. 00:25:16Introduction to SCW Stock Development
  34. 00:25:48SCW Stock Design Principles
  35. 00:26:30SCW Stock Patents
  36. 00:27:09Third SCW Stock Patent and Colt Politics
  37. 00:27:56Greg Grechenko's Original SCW Stock
  38. 00:28:23SCW Stock Folded Position and Width Issue
  39. 00:29:07Production SCW Stock
  40. 00:29:15SCW vs. Standard Bolt Carriers
  41. 00:29:29Finalized SCW Stock Kit Components
  42. 00:30:00Final SCW Stock Design (Open/Contracted)
  43. 00:30:09SCW Stock Folding Mechanism
  44. 00:30:18Finalized Colt SCW Subcompact Weapon
  45. 00:30:30SCW Stock Market Performance
  46. 00:31:22LWRCi Stock Comparison
  47. 00:31:48Legacy of the SCW Stock
  48. 00:32:19Conclusion: M5 and SCW Programs
  49. 00:33:05Recommendations for M5/LE 1020 Enhancements
  50. 00:33:21Colt Patents and Future Potential
  51. 00:33:50Outro and Call to Action

Frequently Asked Questions

What was the Colt M5 rifle?

The Colt M5 was an experimental external piston rifle developed by Colt around 2006-2007. It was designed as a response to the growing popularity of piston-driven AR-15 platforms and featured a 5.56x45mm caliber and a unique heat evacuation system.

Who designed the Colt M5?

The Colt M5 was designed by Greg Grechenko, a brilliant engineer at Colt who drew inspiration from both the AR platform and AK-47 family external piston systems. His initials, GK, are found on the serial number prefix of the M5.

What made the Colt M5's design unique?

The M5 featured a notable heat evacuation system with flutes on the barrel extension and aluminum heat shields, designed to increase cook-off time. It also utilized a standard M4 upper receiver, differing from Colt's one-piece upper used on other piston designs like the LE 1020.

Why was the Colt M5 rifle canceled?

Colt canceled the M5 program in favor of the LE 1020 design, which was considered more mature due to its lineage from the SCAR Type-C and extensive testing. Internal competition between two development teams also contributed to the decision.

What was the SCW stock developed by Colt?

The SCW (Subcompact Weapon) stock was a compact, side-folding stock mechanism developed by Greg Grechenko for Colt firearms. It aimed to reduce the overall length of the weapon but increased its width when folded.

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