From Bench to Range: Testing Your Finished AR-15 80% Lower Build

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Completing an AR-15 80 lower build is a rewarding experience, but the work doesn’t end once your firearm is assembled. Before taking it out for regular use, you need to thoroughly test your build to ensure it functions safely and reliably. Proper testing not only verifies your machining and assembly work but also ensures your firearm is ready for the range or other intended uses.

In this guide, we’ll walk you through the steps to test your finished AR-15 80 lower build, from the bench to the range, covering essential checks, troubleshooting tips, and safety considerations.

Bench Testing Your AR-15 Build

Before heading to the range, perform a series of bench tests to verify the basic functionality of your firearm.

1. Visual Inspection

Start by inspecting your completed firearm for any obvious issues.

Checklist:

  • Receiver Alignment: Ensure the upper and lower receivers fit together snugly without excessive wobble.
  • Machining Accuracy: Check that the fire control cavity and pin holes are cleanly machined with no rough edges.
  • Component Fitment: Verify that all parts, including the trigger, magazine catch, and safety selector, are properly installed.

2. Function Check

Perform a series of dry-fire tests to confirm that the fire control group and safety mechanisms work correctly.

How to Perform a Function Check:

  1. Trigger and Hammer:
    • With the firearm on safe, pull the trigger to ensure it doesn’t release the hammer.
    • Switch to fire, pull the trigger, and confirm the hammer drops.
    • Hold the trigger back, manually reset the hammer, and release the trigger to ensure it resets correctly.
  2. Safety Selector:
    • Ensure the safety blocks the trigger when engaged and allows it to fire when disengaged.
  3. Magazine Release:
    • Insert and remove a magazine to verify the magazine catch works smoothly.
  4. Bolt Catch:
    • Pull the charging handle and engage the bolt catch to lock the bolt back.
    • Release the bolt catch to confirm the bolt moves forward correctly.

Pro Tip: Use snap caps or dummy rounds to test cycling and feeding without using live ammunition.

3. Cycling Test

Manually cycle the bolt carrier group (BCG) to ensure smooth operation.

Key Areas to Check:

  • Bolt Lock-Up: Ensure the bolt locks into the barrel extension securely.
  • Ejection: Pull the charging handle to confirm dummy rounds eject properly.
  • Reset: Verify that the trigger resets after each manual cycle.

Preparing for the Range

1. Safety First

Before firing your AR-15 for the first time, ensure you have the following:

  • Hearing and Eye Protection: Essential for safety at the range.
  • A Clean Workspace: Ensure your firearm is clean and lubricated to reduce the risk of malfunctions.

2. Tools and Spares

Bring a basic toolkit and spare parts in case adjustments or repairs are needed.

Suggested Tools:

  • Multitool or armorer’s wrench.
  • Allen wrenches for optics and accessories.
  • Cleaning kit for quick maintenance.
  • Extra pins, springs, and magazines.

Range Testing Your AR-15 Build

Once you’ve verified functionality at the bench, it’s time to head to the range for live-fire testing.

1. Start with a Single Round

Load and fire a single round to confirm basic functionality.

What to Observe:

  • Bolt Lock-Back: After firing, ensure the bolt locks back if using a magazine.
  • Ejection Pattern: Note where the spent casing lands (typically between 3 and 4 o’clock relative to the shooter).
  • Trigger Reset: Confirm the trigger resets correctly.

2. Test Cycling with a Full Magazine

Load a full magazine and fire several rounds in succession to test cycling and feeding.

Watch for:

  • Failures to Feed: Check that each round is properly chambered.
  • Failures to Eject: Ensure spent casings are consistently ejected.
  • Double-Feeds: Look for any instances of two rounds attempting to load simultaneously.

3. Accuracy Testing

Once basic functionality is confirmed, test your firearm’s accuracy.

Steps:

  1. Use a stable shooting platform or bench rest.
  2. Fire a few groups of 5–10 rounds at a target.
  3. Evaluate shot placement and make adjustments to your sights or optics if necessary.

Pro Tip: Use the same ammunition you plan to use regularly for consistent results.

4. Gas System Tuning (If Applicable)

If your AR-15 is equipped with an adjustable gas block, fine-tune it to optimize performance.

Steps to Adjust:

  1. Start with the gas block fully open.
  2. Gradually reduce gas flow while firing until the firearm reliably cycles and locks back after each shot.
  3. Verify ejection patterns and recoil to ensure smooth operation.

Troubleshooting Common Issues

1. Failure to Feed

Possible Causes:

  • Weak magazine spring or faulty magazine.
  • Insufficient lubrication on the bolt carrier group.

Solution:

  • Test with a different magazine.
  • Clean and lubricate the BCG and receiver.

2. Failure to Eject

Possible Causes:

  • Over- or under-gassed system.
  • Dirty or worn extractor.

Solution:

  • Adjust the gas block if applicable.
  • Inspect and clean the extractor.

3. Light Primer Strikes

Possible Causes:

  • Improperly installed or weak hammer spring.
  • Debris in the trigger assembly.

Solution:

  • Reinstall the hammer spring correctly.
  • Clean the trigger assembly.

4. Excessive Recoil or Bolt Speed

Possible Causes:

  • Gas system is over-gassed.
  • Buffer weight is too light.

Solution:

  • Adjust the gas block to reduce gas flow.
  • Upgrade to a heavier buffer.

Final Thoughts

Testing your AR-15 built from an 80% lower receiver is a critical step in ensuring safety, reliability, and performance. By following these bench and range testing procedures, you can identify and resolve potential issues early, setting the foundation for a firearm you can trust.