RN 50 Caliber Change

Published on September 23, 2022
Duration: 5:43

Mark Serbu, a gun designer, details the process of converting his RN 50 rifle from .50 BMG to 6.5x55 Swedish. This modification involves a custom-machined adapter bushing that threads into the receiver, allowing for the installation of a Savage 10/110 series barrel. The conversion is presented as a practical solution for export challenges and a way to adapt the robust RN 50 platform to a less powerful, more common cartridge.

Quick Summary

Gun designer Mark Serbu details a caliber conversion for the RN 50 rifle, swapping .50 BMG for 6.5x55 Swedish. The process uses a custom adapter bushing (1.5-12 external, 1-1/16-20 internal) to fit a Savage 10/110 barrel, enabling easier export and reduced recoil.

Chapters

  1. 00:00Introduction: RN 50 Caliber Change
  2. 00:29Motivation for Caliber Change
  3. 00:46Previous RN 50 Conversions
  4. 01:05Conversion Method: Adapter Bushing
  5. 01:23Acquiring the 6.5x55 Barrel
  6. 01:44Barrel Features and Finish
  7. 02:166.5x55 Ammunition Anecdote
  8. 02:53Machining the Adapter Bushing
  9. 03:15Bushing Threading Specifications
  10. 03:40Test Firing and Results
  11. 04:57Firing Pin Impression and Conclusion

Frequently Asked Questions

How is the RN 50 converted from .50 BMG to 6.5x55 Swedish?

The conversion involves replacing the original .50 BMG barrel with a new 6.5x55 Swedish barrel. This is achieved using a custom-machined adapter bushing that threads into the RN 50 receiver, providing the correct threading for a Savage 10/110 series barrel.

What are the key specifications for the RN 50 caliber conversion adapter bushing?

The adapter bushing is threaded 1.5-12 externally to match the RN 50 receiver and BFG-50 barrels. Internally, it's threaded 1-1/16-20 to accept a Savage 10/110 series barrel. It's made from 4140/4150 steel with a Rockwell C hardness of 28-32.

Can a .50 caliber firing pin ignite a 6.5x55 Swedish primer?

Yes, the video demonstrates that the .50 caliber firing pin on the RN 50 has no issue igniting the primer of a 6.5x55 Swedish cartridge. The smaller brass marks inside the cap indicate the primer was struck effectively.

What type of barrel is used for the 6.5x55 Swedish conversion on the RN 50?

A 26-inch E. Arthur Brown Company (EABCO) varmint barrel designed for the Savage 10/110 series was used. It features a blued finish, a 1:8 twist rate, and an 11-degree target crown.

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