ARS NOTES
AK TRIGGER ADJUSTMENT.

Page Outline

• Introduction
• Hammer Shelf & Disconnector Claw
• Disconnector Travel
• Hammer Release
• Trigger Reset
• Proof
• Raw Data
• Data Commentary

Since the Arsenal fire-control group is significantly more expensive than the TAPCO, I decided to determine if I could modify the TAPCO G2 to work reliably, safely, and consistently in the NoDak Spud NDS3 receiver.

In some circumstances, with some NDS receivers and some TAPCO G2 fire-control groups, with the trigger pulled in a certain way, the hammer can follow. It is caused by a stacking of the following tolerances.

• receiver rail height
• bolt carrier base
• hammer-trigger hole spacing
• hammer-trigger hole height
• hammer & trigger hole distance from receiver rail
• hammer shelf dimension
• disconnector claw dimension
• disconnector travel dimension

Examining import fire-control groups show some with signs of factory adjustment and numbering to the gun. This indicates fire-control groups are not always interchangeable between guns.

One shooter's trigger manipulation may not result in hammer-follow, while another shooter can get hammer-follow on the same rifle. A solid, fast pull to the rear will rarely get a hammer follow. A slow, smooth pull and holding at the point of hammer release may get a follow.

• I identified the potential problems.
• I created a data-base of fire-control group dimensions.
• I correlated the data to yes/no hammer follow.
• I determined the dimensions that prevented hammer follow
• I determined the adjustments necessary
• I quantified the degree of adjustment
• I proofed my results on 50 rifles.
• I forwarded the data to Nodak Spud and TAPCO for their reference.

The results I obtained are dependent on the slot cut for the 2nd arm of the 2-claw trigger being 4.25mm. This is shorter than the left side cut side cut. If the cut is too long, the trigger can rotate too far forward. The rotating hammer may then hit the TOP of the disconnector, rather than the camming surface on its leading edge. result is disconnector failure (hammer follow). If the cut is too short, the trigger does not travel far enough to release the hammer. While other lengths will work, 4.25mm is the constant I used to isolate the hammer to disconnector dimensions.

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PROBLEM.

SOLUTION.

DETAILS.

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PROBLEM.

SOLUTION.

DETAILS.

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PROBLEM.

SOLUTION.

DETAILS.

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PROBLEM.

SOLUTION

DETAILS

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• I assembled 30 trigger-disconnector groups
• I adjusted the gap to approximately .350"
• I marked their dimensions on the assemblies
• I modified 30 hammer shelves to approximately .420"
• I marked the dimension on the side of the hammer
• I paired hammers with trigger-disconnector assemblies to those with 15% differences

All 30 guns yielded a disconnector gap ranging from slight contact to .008" Most were 0 to .005". a few needed the hammer shelf radiused slightly - the disconnector didn't stop the hammer from releasing but there was slight rubbing. I have complete 60 rifles and cannot coax any of them to hammer follow. I understand that this is a small statistical sampling. I will update my results if further data collection suggests a different adjustment process.

Update. 350 trigger groups testfired with the above adjustments. Zero doubling. 2 with drag on disconnector release requiring a slight breaking of the "hawk beak" edge on disconnector.

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Target trigger gap of .0.360" - .0100"

Typical hammer width after reducing shelf: 0.415"-0.005"

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