The Rock River Arms LAR47 Rifle Technical Review

Published on September 3, 2018
Duration: 28:50

This technical review of the Rock River Arms LAR-47 rifle, chambered in 7.62x39mm, highlights its design to reliably use AK-type magazines. The presenter, an experienced firearms instructor, details the proprietary receivers, chrome-lined barrel, and bolt carrier group, while also discussing the historical challenges of adapting AR-15 platforms to this caliber, particularly concerning magazine feeding and primer sensitivity.

Quick Summary

The Rock River Arms LAR-47 is designed to reliably fire the 7.62x39mm cartridge using AK-type magazines, overcoming historical feeding issues with proprietary receivers. It features a chrome-lined barrel, a heavier hammer spring for hard primers, and a bolt carrier group with a bolt machined for the caliber, though bolt durability remains a point of industry discussion.

Chapters

  1. 00:06Introduction to AR-15s with AK Magazines
  2. 00:25History of 7.62x39mm AR Prototypes
  3. 01:48The Magazine Feeding Challenge
  4. 02:04AK vs. AR Magazine Feed Geometry
  5. 03:19Colt's 7.62x39mm Attempts
  6. 03:47Hybrid Magazine Issues
  7. 04:15Aftermarket 7.62x39mm AR Magazines
  8. 05:00Rock River Arms LAR-47 Introduction
  9. 05:51RRA's Design Philosophy: AK Magazine
  10. 06:11LAR-47 Receiver and BCG Overview
  11. 07:04Free-Floating Handguard and Rails
  12. 07:44Front Sight Base and Sling Swivels
  13. 08:03Critique: Bolt-On Front Sight Base
  14. 08:48Barrel Specifications and Muzzle Brake
  15. 09:11Proprietary Stock and Receiver Extension
  16. 09:37AK Magazine Compatibility Discussion
  17. 10:37Common Magazine Fitment Issues
  18. 11:34Magazine Tab Length Variance
  19. 11:56LAR-47 Magazine Compatibility Test
  20. 13:52Internal Components: Stock and Receiver
  21. 14:39Pistol Grip and Magazine Release
  22. 15:01Forward Assist and Case Deflector
  23. 15:09Bolt Carrier Notch Indicator
  24. 15:34Optic: Sig Sauer Bravo 4
  25. 16:23Absence of Bolt Catch
  26. 16:33Rock River Arms Enhanced Safety Selector
  27. 17:04Takedown and Pivot Pin Upgrades
  28. 17:20Upper Receiver and Handguard Details
  29. 17:47Internal Receiver Components
  30. 17:56Primer Sensitivity and Firing Pin
  31. 18:32Heavier Hammer Spring Solution
  32. 19:25Receiver Machining and Trigger
  33. 19:45Upper Receiver Cut for Auto Sear
  34. 19:56Bolt Carrier Group Details
  35. 20:41Bolt Machining for 7.62x39mm
  36. 21:09Bolt Durability Concerns
  37. 21:28Alternative Bolt Designs (Colt, CMMG)
  38. 21:53Component Compatibility Advantages
  39. 23:02LAR-47 vs. CMMG Mutant: Parts Availability
  40. 23:57Craftsmanship and Reliability
  41. 24:14Chamber Feed Ramps
  42. 24:31Overall Impression and Price
  43. 24:44Range Test Preview

Frequently Asked Questions

What are the main challenges in adapting AR-15 platforms to the 7.62x39mm cartridge?

The primary challenges historically have been magazine feeding reliability due to the 7.62x39mm cartridge's taper and stacking in standard AR magazines. Additionally, some ammunition features hard primers that can cause light strikes in AR-15 firing pin systems.

How does the Rock River Arms LAR-47 address the 7.62x39mm cartridge and AK magazine compatibility?

The LAR-47 uses proprietary receivers designed for AK magazines. It also features a heavier hammer spring to reliably ignite harder primers and a chrome-lined barrel for durability and corrosion resistance.

What are the key internal components and design features of the Rock River Arms LAR-47?

It has a chrome-plated bolt carrier group, a bolt machined for 7.62x39mm, a two-stage trigger, and a six-position receiver extension. Notably, it lacks a bolt catch due to the AK magazine design and includes a cartridge case deflector.

How does the Rock River Arms LAR-47 compare to other 7.62x39mm AR-style rifles like the CMMG MK47 Mutant?

The LAR-47 is noted for having more industry-standard compatible parts, particularly in the bolt carrier group and handguard, which aids in parts availability. The CMMG MK47 is considered more beefed up for the cartridge but has more proprietary components.

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