Handloading PART VI, How to Measure Cartridge Overall Length ~ GunBlue's Complete Guide

Published on March 4, 2016
Duration: 38:10

This guide details a cost-effective DIY method for measuring Cartridge Overall Length (COAL) using common reloading tools like dial calipers and Scotch tape. The technique, demonstrated by an expert, involves using a cleaning rod to find the maximum COAL for a specific rifle and bullet combination, allowing for precise adjustments to improve accuracy and ensure safe chambering. It emphasizes understanding SAAMI standards and the importance of bullet jump.

Quick Summary

Learn a cost-effective DIY method to measure Cartridge Overall Length (COAL) using a cleaning rod, tape, and dial calipers. This technique helps determine the maximum COAL for your specific rifle, allowing you to set optimal bullet jump (0.015-0.030 inches) for improved accuracy and safe chambering, referencing SAAMI standards.

Chapters

  1. 00:00Introduction to COAL Measurement
  2. 01:00Understanding COAL Standards
  3. 03:38Factors Limiting COAL
  4. 07:30The Cardinal Rule of Seating Depth
  5. 10:00Bullet Jump and Accuracy
  6. 13:55The DIY Measurement Process
  7. 15:54Calculating Maximum COAL

Frequently Asked Questions

What is Cartridge Overall Length (COAL) and why is it important?

COAL is the measurement from the cartridge base to the bullet tip, crucial for safe chambering, magazine feeding, and optimal accuracy. SAAMI sets these standards, but individual rifle chambers and magazines can necessitate custom COAL measurements for handloaded ammunition.

How can I accurately measure COAL without expensive tools?

You can use a simple DIY method with a cleaning rod, Scotch tape, and dial calipers. Mark the rod at the muzzle after seating a bullet against the rifling, then again at the bolt face, and measure the distance between marks to find your rifle's maximum COAL.

What is 'bullet jump' and how does it affect accuracy?

Bullet jump is the free space between the bullet's ogive and the rifling lands. A small, consistent jump (typically 0.015-0.030 inches) often improves accuracy by allowing the bullet to stabilize before engaging the rifling, preventing pressure spikes.

Where can I find standard COAL measurements for my cartridges?

Reliable reloading manuals, such as the Lyman #49th Edition Reloading Handbook, provide SAAMI-specified COAL dimensions for various cartridges. However, always verify these measurements against your specific firearm for optimal results.

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