American Built Custom .750 Low Profile Adjustable Steel Gas Block Tuning

ABC Rifle Company

.750 Adjustable Gas Block – Tuning Guide

Adjustment Basics

The front adjustment screw regulates gas flow to the bolt carrier group (BCG).

Clockwise (IN) Reduces gas flow Counterclockwise (OUT) Increases gas flow

The SIDE set screw secures the adjustment. 

Allen Hex Tool .050 Required

Gas Tuning Instructions

Close the Front Adjustment Screw

Turn clockwise until fully closed (do not overtighten)
Open 1 Full Turn
Provides a baseline to begin tuning
Load & Fire One Round
Use one round in a magazine
No bolt lock-back? Open another ½ turn
Bolt locks back? Proceed to final adjustment
Fine-Tune
Continue in ½-turn increments until the bolt locks back reliably
Add ¼–½ Turn for Reliability
Ensures consistent function with various ammo and fouling

Lock the Setting

This gas block includes a side set screw to secure your adjustment.

Tighten the SIDE set screw gently once tuning is complete- Clockwise (IN)

Do not overtighten — hand-tight is sufficient

Light Threadlocker is recommended

Final Function Check

Fire a short string (5–10 rounds) to confirm:

Smooth cycling
Consistent ejection pattern
Bolt locks back on an empty magazine(after last shot is fired)