This Lower Parts Kit (LPK) consists of an ALG Defense ALG Combat Trigger (ACT) Trigger, paired with a Spike's Tactical parts kit (SLPK100) to make a complete LPK.
ALG Combat Trigger (ACT)
The ALG Defense ALG Combat Trigger (ACT) is designed for those shooters where tradition, value and regulatory concerns are of primary importance. The pull of the ACT is very similar to a standard mil-spec trigger, however it is sharper and the grittiness of the stock trigger pull has been removed while the traditional reliability of a stock trigger remains. The pull weight is not lower than the M4/M16 minimum weight specification of 5.5lbs.
- The ALG Defense ACT trigger pull is smoother and
sharper than a stock trigger. This is accomplished by
polishing the sear surfaces smooth and HardLubing the
- Sear geometry has not been changed from the
standard profile so the high reliability that the stock trigger
is known for is unchanged.
- Trigger and hammer are made from true 8620 alloy
steel military specification castings, correctly carburized,
quenched and tempered for high surface hardness.
- Disconnector is 1070 High Carbon steel properly
Austempered into the spring range of hardness.
- Springs are corrosion resistant and meet military
- A full force hammer spring is used for positive ignition
of all type of ammunition.
- Trigger and hammer pins are improved over stock mild
steel by using 4140 Chrome-Moly steel that has been
quenched and tempered. Pins are centerless ground to
a fine finish and a diameter 0.001” larger than stock to
reduce play in the trigger assembly while retaining a slip fit
into the weapon lower receiver. Both pins are Nickel-Teflon
- Pull weight is above the U.S. Military minimum pull
weight of 5.5lbs but does not reach near the upper limit of
9.5lbs. Generally, the pull weight is about 6.0lbs.
- As a trigger meeting the essential U.S. Military
trigger specifications for the M4 Carbine, the ALG Defense
ACT can be substituted for lower performing stock triggers
while still staying in compliance with Unit or Departmental
Note about HardLubing:
HardLubing is ALG's term for electroless Nickel plating with
an integral modifier to the base nickel plate. Either Boron
or Teflon is used to enhance surface hardness, wear
resistance and corrosion resistance and also create
favorable tribological properties of the trigger components.
Testing has shown that differential coating of the
trigger parts contributes to the sharpness of the ACT's
single stage pull. The trigger component is plated with
Nickel-Boron which has a high surface hardness combined
with excellent wear resistance. The color is a pleasing
matte light grey that may be painted on non-functional
surfaces if the shooter so desires (such as the trigger bow
that is visible outside the lower receiver). The hammer,
disconnector and trigger/hammer pins are plated with
Nickel-Teflon which combines a low coefficient of friction
with good wear resistance. The Teflon impregnation colors
the metal a mottled, greyish/green. Parts coated with
Nickel-Teflon cannot be painted. Both coatings are highly
corrosion resistant eliminating the oil seal of traditional
phosphated firearm components.