300 Blackout - 135gr Sierra Varminter

Published on August 26, 2017
Duration: 35:09

This video details a reloading and range test of 135gr Sierra Varminter bullets in .300 Blackout. The host explores IMR 4227 and Winchester 296 powders, encountering significant pressure signs with Win 296 and cycling issues with IMR 4227. Bullet setback due to insufficient neck tension was identified as a major accuracy impediment.

Quick Summary

Reloading 135gr Sierra Varminter bullets for .300 Blackout revealed issues with IMR 4227 causing cycling failures and Winchester 296 showing dangerous pressure signs. Bullet setback due to poor neck tension significantly impacted accuracy.

Chapters

  1. 00:00Introduction & Component Selection
  2. 02:01Load Data & Case Capacity Issues
  3. 04:21Bullet Seating & Quality Control
  4. 07:46Crimping & Bullet Setback Problems
  5. 11:03Range Test: IMR 4227 Performance
  6. 13:36Range Test: Winchester 296 & Pressure Signs
  7. 15:26Final Analysis & Future Testing

Frequently Asked Questions

What were the key reloading components used for the .300 Blackout test?

The test utilized 135gr Sierra Varminter bullets, new Gemtech brass, CCI 41 primers, and tested two powders: IMR 4227 and Winchester 296 (H110).

What accuracy was achieved with the IMR 4227 load?

When single-loaded to avoid cycling issues, the 19.0gr IMR 4227 load produced a promising 0.61-inch group, indicating potential accuracy if mechanical problems are resolved.

What pressure signs were observed with Winchester 296?

Significant pressure signs were noted with Winchester 296, including ejector swipes and a blown primer pocket at 18.4gr, suggesting 18.0gr was the safe maximum.

What caused bullet setback in the reloaded .300 Blackout cartridges?

Bullet setback was caused by insufficient neck tension from the reloading dies, allowing the bullet to be pushed deeper into the case when the bolt was dropped.

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