.308 Win - 175gr Sierra Match King with IMR 4064 (part 2)

Published on June 11, 2018
Duration: 29:16

This guide details advanced reloading techniques for the .308 Winchester cartridge, focusing on achieving performance comparable to Federal Gold Medal Match using 175gr Sierra Match King bullets and IMR 4064 powder. The expert-level instruction covers critical aspects like brass case capacity analysis, chamber dimension comparisons, and meticulous load development, including suppressed and unsuppressed range testing. It emphasizes understanding pressure signs and mechanical timing issues in semi-automatic platforms.

Quick Summary

Reloading .308 Winchester with 175gr Sierra Match King bullets and IMR 4064 powder requires careful attention to brass case capacity and potential pressure differences. Testing showed that Lapua brass has higher capacity than IMI brass. The best accuracy achieved was a 0.902" group at 42.4 grains, fired unsuppressed, while suppressed testing revealed mechanical timing issues over pressure signs.

Chapters

  1. 00:00Project Overview & Load Goals
  2. 01:27Brass Selection & Case Capacity Analysis
  3. 06:45Chamber Dimensions & Resizing Considerations
  4. 12:01Suppressed Range Testing & Velocity
  5. 18:26Unsuppressed Range Testing & Accuracy
  6. 22:41Brass Inspection & Pressure Signs Analysis
  7. 24:39Conclusion & Future Testing Plans

Frequently Asked Questions

What is the recommended load data for .308 Win using 175gr Sierra Match King bullets and IMR 4064 powder?

The test focused on working up from 42.0 grains to 42.8 grains of IMR 4064 with 175gr Sierra Match King bullets in .308 Winchester. The best accuracy was achieved at 42.4 grains, yielding a 0.902" group unsuppressed.

How does brass case capacity affect reloading pressure in .308 Winchester?

Brass with higher case capacity, like Lapua (56.0gr water weight), allows for more powder space, potentially leading to lower pressures compared to brass with less capacity, such as IMI (53.4gr). Using lower-capacity brass with loads developed for higher-capacity brass can significantly increase pressure.

What are common pressure signs to watch for when reloading .308 Winchester, especially in an AR-10?

While flattened primers can indicate pressure, ejector swipes and brass burrs observed in suppressed AR-10 platforms often point to mechanical timing issues rather than excessive pressure. Round primers generally suggest the latter.

What was the best accuracy achieved in the .308 Win reloading test with 175gr Sierra Match Kings?

The most accurate group recorded during the test measured 0.902 inches. This was achieved with a load of 42.4 grains of IMR 4064 powder, using a 175gr Sierra Match King bullet, fired unsuppressed.

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