308 Win - 165gr Hornady GMX with AR-Comp

Published on October 21, 2021
Duration: 24:03

This video details the process of developing a hunting load for the 308 Winchester using 165-grain Hornady GMX bullets and AR-Comp powder. The instructor systematically adjusts the overall length (OAL) of the cartridges, starting from 2.740 inches and decreasing in 0.010-inch increments, while maintaining a consistent powder charge. Ballistics data, including velocity and group sizes, are recorded and analyzed at each step to identify the most accurate and reliable load for hunting in thick woods. The process also includes insights into brass preparation and sizing die selection.

Quick Summary

For 308 Winchester loads using 165gr Hornady GMX bullets and AR-Comp powder, an overall length (OAL) of 2.720 inches was selected for hunting. This length provided a good balance of accuracy and point of impact stability, with groups averaging around 1.32 inches at 100 yards and velocities near 2696 fps.

Chapters

  1. 00:00Introduction: 308 Win GMX & AR-Comp Reloading
  2. 00:04Recap of Previous Reloading Issues
  3. 00:18Previous Group Results & Lead-Free Bullet Struggles
  4. 00:41Velocity Drop with Shorter OAL for GMX Bullets
  5. 01:17Hypothesis: Dropping Charge Weight vs. OAL
  6. 01:30Plan: Stick to 42.4 Grains AR-Comp, Vary OAL
  7. 02:00Bullet Count & Hunting Ammunition Needs
  8. 02:43Reloading Components: AR-Comp, Brass, Primers
  9. 02:55Brass Preparation: Annealing
  10. 03:05Sizing Die Comparison: Hornady vs. RCBS
  11. 04:06Neck Diameter Measurements
  12. 04:51Body Diameter Measurements Below Shoulder
  13. 05:39Comparison Summary: RCBS vs. Hornady Sizing
  14. 05:53Testing Redding Fulling Sizing Die
  15. 07:10Setting Sizing Die Bump
  16. 07:54Expander Die Setup & Observation
  17. 09:27Loading Sierra Match King for Palate Cleanser
  18. 10:37Sierra Match King Load Details
  19. 10:41Loading Hornady GMX: First OAL (2.740")
  20. 11:36Bullet Seating Feel & Driving Bands
  21. 13:16Possible Cause for Seating Feel: Compressed Load
  22. 14:17Reloading Session Progress & Comparison to Last Video
  23. 14:46Neck Tension Options: .306 Expander vs. Larger
  24. 15:17Range Day: Setup & Equipment
  25. 15:33Rifle & Scope Specifications
  26. 15:57First Group: OAL 2.740" (Verification)
  27. 16:26Results: 1.17" Group, 2709 fps
  28. 17:10Second Group: OAL 2.730"
  29. 17:38Results: 1.27" Group, 2699 fps
  30. 17:49Third Group: OAL 2.720"
  31. 18:22Results: 1.32" Group, 2696 fps (with outlier)
  32. 18:36Fourth Group: OAL 2.710"
  33. 19:03Results: 1.39" Group, 2690 fps
  34. 19:10Analysis of Group Performance & Point of Impact
  35. 19:38Palate Cleanser: Sierra Match King Group
  36. 20:09Sierra Match King Results: 0.75" (with outlier)
  37. 20:40Testing Factory Ammo: Hornady BTHP
  38. 21:18Factory Ammo Malfunction & Analysis
  39. 22:00Decision: Selecting the 2.720" OAL Load for Hunting
  40. 22:37Future Updates & Hunting Season
  41. 22:45Thanks to Viewer Clint for Bullet Donation
  42. 23:13AR10 308 Project Progress & Future Plans
  43. 23:25Upcoming 6.5 Creedmoor AR-10 Videos
  44. 23:35Next Video Preview: 223 Rem & 75gr Hornady
  45. 23:48Powder Diversity & Future Content

Frequently Asked Questions

What is the recommended overall length for 308 Winchester loads using 165gr Hornady GMX bullets and AR-Comp powder?

For 308 Winchester loads with 165gr Hornady GMX bullets and AR-Comp powder, the optimal overall length (OAL) was found to be 2.720 inches. While 2.740 inches yielded a slightly smaller group, 2.720 inches offered better consistency and point of impact stability for hunting purposes.

How does overall length affect velocity and accuracy with 165gr Hornady GMX bullets in 308 Winchester?

With 165gr Hornady GMX bullets in 308 Winchester, decreasing the overall length from 2.740 inches to 2.720 inches showed a slight decrease in velocity but improved group consistency. Shorter OALs can sometimes lead to velocity drops with lead-free bullets, but in this case, accuracy improved as the length decreased.

Which sizing die is recommended for reloading 308 Winchester brass with Hornady GMX bullets?

For reloading 308 Winchester brass with Hornady GMX bullets, the RCBS small base sizing die is recommended over the Hornady custom grade die. The RCBS die worked the brass less, resulting in easier sizing and a less compressed neck, which can be beneficial for consistent seating.

What are the key components for developing a 308 Winchester hunting load with AR-Comp powder?

Key components for developing a 308 Winchester hunting load with AR-Comp powder include 165-grain Hornady GMX bullets, Lapua Palma brass, and CCI 41 primers. The powder charge used was 42.4 grains, with overall lengths tested ranging from 2.740 to 2.710 inches.

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