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Note: It is better to repeat step 3 many times in small increments, checking the clearance of the gage pin each time to ensure a proper, safe fit.

THE WISCONSIN TRIGGER COMPANY, INC. MANUFACTURED MILAZZO-KRIEGER M-K II AR15 TWO STAGE MATCH TRIGGER SYSTEM INSTALLATION AND ADJUSTMENT PROCEDURES.

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When ordering please let us know if you would like to take advantage of this service.

Installation Instructions

WARNING: This trigger system is designed to be installed by a professional and competent gunsmith for use in a firearm. If you are not a professional, competent gunsmith, DO NOT attempt installation. Contact a professional, competent gunsmith to proceed further. This trigger system requires precise custom fitting for the firearm to remain safe and reliable.

Warning: Due to dimensional variations of receivers and safeties, specific critical areas of our trigger system parts have been left oversize to permit the precise fitting needed to obtain a true “MATCH GRADE” trigger. The fitting of this trigger system requires the skills of a competent gunsmith, who has had extensive experience working with AR15 style rifles and who thoroughly understands trigger systems in addition to the potential dangers involved with a trigger that has not been properly installed, adjusted, and safety tested.

Due to the fact that we have no control over the way our parts are installed or used, The Wisconsin Trigger Company, Inc. makes no representation or warranties whatsoever, other than those listed on The Wisconsin Trigger Company, Inc. website. The Wisconsin Trigger Company, Inc. claims no assumption of liability, either expressed or implied, for damage or injury which results from the installation, use, or possession of these parts, and the user assumes all such risk.

The user is expressly warned that after installation of the trigger system into a firearm, the firearm will discharge with less effort. The fact that this is a two stage trigger means the feel will differ greatly from the original single stage unit. This trigger system is specifically designed for competitive match shooting purposes on controlled firing ranges only under direct supervision of a trained and professional range specialist.

Additionally, as with any mechanical object, wear will occur. This can affect the integrity of the system. The user must be aware that if the trigger pull weight or feel of the trigger should change they must DISCONTINUE USE IMMEDIATELY. Do not use the firearm again until cause of such change has been identified and safely remedied by a professional and competent gunsmith.

DANGER! DO NO ATTEMPT TO SET THE TRIGGER PULL WEIGHT BELOW 3 ¼ LBS. Under NO circumstances should the rifle be fired if the trigger pull is below 3 ¼ lbs. (SR25, 4 lbs. minimum)

Illustration A-1

Illustration A-1

DO NOT attempt disassembly of the disconnector from the trigger body. A new disconnector pin must be fitted and installed whenever the disconnector pin has been removed for any reason. Failure to do so can compromise the safety of the system. If you feel that the disconnector is not functioning properly in any way, follow the warranty return instructions on The Wisconsin Trigger Company, Inc. website.

DO NOT attempt to reduce trigger pull weight by reducing tension of the disconnector spring or by replacing with a spring other than those supplied by The Wisconsin Trigger Company, Inc.

Disassembly for routine cleaning is neither needed nor recommended, as it will only accelerate wear of the hammer and trigger pin holes in the receiver. We recommend cleaning with Hoppes #9 or CLP and lube with CLP. DO NOT use spray type cleaning agents. DO NOT use grease as a lubricant.

Note: Fitted trigger is not interchangeable with any other receiver. Replacement of any part will require full refitting of the trigger system.

M-K II – INSTALLATION INSTRUCTIONS

DO NOT PROCEED UNTIL YOU HAVE READ AND UNDERSTAND ALL OF THE INSTRUCTIONS AND ARE A COMPETENT AND PROFESSIONAL GUNSMITH.

Steps must be followed and completed in the order shown.

DISASSEMBLY

  1. CLEAR RIFLE. Be sure that is unloaded.
  2. Separate upper and lower assemblies. Set upper assembly aside.
  3. Disassemble lower receiver:
    • Remove pistol grip
    • Remove safety selector, selector detent spring, and selector detent
    • Remove hammer
    • Remove trigger
  4. Compare original hammer and trigger pins to the new pins to make sure you have the correct size pins for your receiver.
  5. Set aside original hammer, trigger, hammer and trigger springs, disconnector, and disconnector spring. These will not be used in your new trigger system. Safety selector, selector detent, and selector detent spring will be reinstalled. Replace if these have been altered in any way.

(Note: Original pins are just a few thousandths smaller in diameter than new pins and will be used throughout most of the fitting procedures to avoid wearing the pin holes in the receiver. Final setup and tests MUST be done with M-K II pins in place.)

CONFIRM DISCONNECTOR SPRING

Before installation, confirm the disconnector spring you wish to use is properly installed in the trigger housing. Consult the Disconnector Spring Chart located in the parts box (Illustration “A-1” above). All M-K II triggers systems come from the factory with the Blue medium spring installed. If you wish to change spring please see the directions below. It is best to complete this before installation of the M-K II to avoid undue wear to the receiver pin holes.

Small Pin Model M-K II Triggers

  1. Remove the Spring Plug from the bottom of the Trigger Housing and remove existing Disconnector Spring through the Spring Plug Hole.
  2. Install the desired Disconnector Spring through the Spring Plug Hole and seat it on to the Spring Tab of the Disconnector.
  3. Reinstall the Spring Plug in the bottom of the Trigger Housing using Loctite to hold it in place. The Spring Plug must be installed flush with the outside bottom of the Trigger Housing. Installing too deep will add unwanted trigger pull weight. Installing too shallow will interfere with trigger movement.
  4. Proceed with the fitting and installation of the Trigger Housing.

Large Pin Model M-K II Triggers

  1. Remove existing Disconnector Spring by lifting the bottom of the Spring with a small flathead screwdriver and prying rearward.
  2. Install the new Disconnector Spring on to the Spring Tab of the Disconnector and push the bottom of the Disconnector Spring in place with a small Flathead screwdriver.
  3. Proceed with the fitting and installation of the Trigger Housing

INSTALLATION AND ASSEMBLY

  1. Clean and carefully inspect lower receiver and any components that are to be reused for damage or alteration. All parts MUST be undamaged and unaltered. Check receiver for any engagement or overtravel limiting screws or blocks. These must be removed.
  2. Fit new trigger spring and install M-K II trigger assembly into receiver. Push original pin in from left to right.
  3. Fit new hammer spring and install M-K II hammer assembly into receiver. Spring legs must go on top of trigger pin. Use old pin (install from right to left) for trial fitting.
  4. Set second stage engagement:

“0” (baseline) second stage engagement point is determined by carefully pulling the trigger and turning the adjusting screw clockwise (CW) by 1/16 turn increments until no stop is detected before the hammer is released when the trigger is pulled. NEVER FIRE OR DRY FIRE THE RIFLE WITH THE ADJUSTING SCREW BACKED OUT LESS THAN 3/8 TURN COUNTER-CLOCKWISE (CCW) FROM THIS “0” POINT.

To increase second stage engagement: Turn adjusting screw CCW. DO NOT set engagement to more than 1 ¼ turns out CCW from “0” second stage engagement point.

After the second stage engagement has been established, Loctite must be applied, as per Loctite instructions, to the threads of the adjustment screw. Whenever the screw is moved or readjusted follow Loctite instructions for cleaning and reapplying of Loctite. If properly adjusted, readjustment is rarely needed.

FITTING THE SELECTOR SWITCH

  1. With hammer cocked, determine metal to be removed from surface “D-E” (fig. 1) to allow a 3/8” dia. gage pin to pass through the receiver without binding the trigger. Surface “D-E” has been intentionally left oversize to allow for precise fitting into the receiver.

CAUTION: This will also affect overtravel and any additional clearance will also decrease the amount of safety engagement. PROCEED CAREFULLY!

  1. Remove hammer, and trigger assemblies from receiver.
  2. File or polish surface “D-E” to dimension determined in step 1. Use angle shown in figure 1.
  3. Clean parts and reassemble. The gage pin will not install unless the hammer is cocked. With the gage pin in place and the hammer cocked, the trigger should have some free-play.

Note: It is better to repeat step 3 many times in small increments, checking the clearance of the gage pin each time to ensure a proper, safe fit.

  1. Remove the gage pin and lube system with CLP.
  2. While controlling the hammer pull the trigger to make sure that the hammer will fall when the trigger is pulled. If the hammer will not fall check for overtravel limitation (i.e. interference) in the receiver. Make sure the hammer will fall with at least .015” overtravel before proceeding.
 
 
  1. Recock the hammer and install the selector switch.
  2. Install the pistol grip with the selector detent and detent spring properly positioned. Check the selector switch to make certain it is positively and consistently locating in the same position in both “SAFE” and “FIRE” mode. Set the selector to the “SAFE” position and check function. The trigger should be able to move slightly but the disconnector must have at least .025” clearance with the rear hammer hook when the trigger is pulled firmly to the rear.
  3. Set safety to “FIRE” position while controlling the hammer and pull the trigger. If the hammer will not release the surface “D-E” on the trigger or depth of notch “F” in the selector switch will need to be carefully cut until the trigger has at least .005” overtravel. If the hammer will not fall fully forward, refer to fitting tips at the end of the instructions.

Note: Over-cutting of surface “D-E” can cause the firearm to become unsafe. If the hammer will not fall fully forward, refer to fitting tips at the end of the instructions.

Note: Increasing depth of notch “F” requires removal from the receiver of the selector switch only, and maintains maximum safety engagement. If notch “F” is cut deeper, it CANNOT be safely used again with the standard trigger system.

WARNING: Alteration of selector switch at any point other than notch “F” can cause firearm to become unsafe.

  1. Recock the hammer and set the safety to “Fire” position. Slowly and carefully pull the trigger through the first stage only. Any coarse feeling in the trigger will disappear within the first 75 to 100 firings. The trigger should come to a distinct and positive stop when the disconnector contacts the hammer. From this point:
  • Releasing the trigger should allow it to return to the start of the first stage engagement point.
  • Additional pull of the trigger should allow the hammer to release, only after the desired pull weight is reached.
  1. Lubricate ALL contact areas, pins, and working parts with CLP or equivalent only. DO NOT USE GREASE.
  2. Test safety engagement, disconnector, and overtravel for proper function.
  3. Reassemble upper receiver to lower receiver and slowly cycle the bolt fore and aft to check cocking and firing pin clearance to hammer notch “J”. ZERO CONTACT IS PERMITTED.
  4. Check to make sure that the bolt cycles freely with the trigger held in the fired position (rear). If any bind is encountered check the hammer spring for proper installation. Excess overtravel can also be a cause of this problem.
  5. If all tests prove OK, go to a safe firing range and carefully test-fire the rifle until you are familiar with the new trigger and are absolutely certain that all aspects and safeties are functioning properly.

FITTING TIPS

Receiver

  • Check for over/undersized, misaligned, or improperly positioned pin holes.
  • Lap undersized holes. DO NOT REAM.
  • For oversized, misaligned, or improperly positioned holes, contact lower receiver manufacturer.

Selector switch

  • Inconsistent detent operation. Check detent spring and detent for proper installation or excessive wear.
  • Check selector switch for notches with burs, parting lines, or other offsets that interfere with trigger motion.

Trigger pull weight

  • Variation is likely a result of trigger/hammer spring inconsistencies.
  • Trigger pull weight can be increased be equally bending both trigger spring legs down.
  • IMPORTANT: Bend at or up to 1/8” forward of the point where the lower spring legs exit the wind of the spring that goes around the trigger boss. DO NOT bend spring legs up to reduce pull weight. Spring must have a kinked bend when properly done. See fig. 2.
 
 

Hammer

  • With overtravel correct, if hammer does not travel fully forward, check for interference with cam “G” (see fig. 1). If all adjustments have been correctly done and interference still exists cam “G” must be reduced. CAUTION: Excessive removal of material at cam “G” can cause an unsafe condition and damage the firearm. Trigger should have slight free play in the fired position.
  • If firing pin catches hammer notch “J” check to make sure that an AR15 firing pin has been installed in the BCG. Firing pins of any other type can cause interference.
  • Reduce hammer notch “J” only as a last resort, and then only enough to clear firing pin collar to ensure smooth bolt closing (see fig. 1).

INSTALLATION INSTRUCTIONS

M-K IIA2 Large and Small Pin Models

DO NOT PROCEED UNTIL YOU HAVE READ AND UNDERSTAND ALL OF THE INSTRUCTIONS AND ARE A COMPETENT AND PROFESSIONAL GUNSMITH.

Steps must be followed and completed in the order shown.

DISASSEMBLY

  1. CLEAR RIFLE. Be sure that is unloaded.
  2. Separate upper and lower assemblies. Set upper assembly aside.
  3. Disassemble lower receiver:
    • Remove pistol grip
    • Remove safety selector, selector detent spring, and selector detent
    • Remove hammer -Remove trigger
  4. Set aside original hammer, trigger, hammer and trigger springs, disconnector, disconnector spring and 2 receiver pins. These will not be used in your new trigger system.
  5. Retain the pistol grip, safety selector, selector detent, and selector detent spring. They will be reinstalled. Replace any of these items if they have been altered in any way.

CONFIRM DISCONNECTOR SPRING

Before installation, confirm the disconnector spring you wish to use is properly installed in the trigger housing. Consult the Disconnector Spring Chart located in the parts box (Illustration “A-1” ). All M-K IIA2 triggers systems come from the factory with the Blue medium spring installed. If you wish to change spring please see the directions below. It is best to complete this before installation of the M-K II to avoid undue wear to the receiver pin holes.

Trigger pull weight

  • Variation is likely a result of trigger/hammer spring inconsistencies.
  • Trigger pull weight can be increased be equally bending both trigger spring legs down.
  • IMPORTANT: Bend at or up to 1/8” forward of the point where the lower spring legs exit the wind of the spring that goes around the trigger boss. DO NOT bend spring legs up to reduce pull weight. Spring must have a kinked bend when properly done. See fig. 2.
 
 

INSTALLATION AND ASSEMBLY

  1. Clean and carefully inspect lower receiver and any components that are to be reused for damage or alteration. All parts MUST be undamaged and unaltered. Check receiver for any engagement or overtravel limiting screws or blocks. These must be removed.
  2. Fit new trigger spring to the M-K II trigger and install M-K II trigger assembly into receiver. Using one of the new supplied pins, install from left to right.
  3. Fit new hammer spring  to the M-K II hammer and install M-K II hammer assembly into receiver. Using one of the new supplied pins, install from left to right with the groove on the pin going in last.  The spring legs must go on top of trigger pin.
  4. Reinstall the safety selector, safety selector detent,  detent spring and pistol grip.
    Set second stage engagement:

Note: It is extremely important that the “0” second stage engagement point be accurately established before making any other adjustments.

 
 

Determine the Zero “0” Baseline

  1. The Zero  “0” Baseline second stage engagement point is determined by carefully pulling the trigger and turning the adjusting screw clockwise (CW) by 1/16 or less turn increments until no stop is detected before the hammer is released when the trigger is pulled. At this point you have no second stage engagement. This is the Zero “0” Baseline point. The more accurately you get to this point the better the end result will be. Do not rush this. Turn the adjusting screw slowly and check for the hammer release with every adjustment. Turn the adjusting screw in and out a few time to get the feel for it and when you make your final adjustment go as slowly as you can. You can see a video of this on The Wisconsin Trigger Company, INC web site.  WWW. WisconsinTrigger.com

NEVER FIRE OR DRY FIRE THE RIFLE WITH THE ADJUSTING SCREW BACKED OUT LESS THAN 3/8 TURN COUNTER-CLOCKWISE (CCW) FROM THIS Zero “0” POINT

  1. With the 0 point set turn the adjusting screw  3/8 of a turn out CCW.
    • Safety Note: DO NOT set engagement to less than 3/8 turn out CCW from “0” second stage engagement point. Insufficient engagement can cause inconsistent discharge feel, accelerate wear, and/or damage the trigger system parts. It is also a safety concern.
  2. Without letting the hammer hit the receiver test the pull and release of the trigger. If you have a good second stage release and a noticeable,  well defined  wall at the end of the first stage continue on to check the safety engagement. If all the checks are satisfactory go on to step 4 . If any of the check are not satisfactory go back to step 1 and start over.
  3. Make a mark on the top of the adjusting screw that lines  up with a point on the receiver and note this point.
  4. Back the adjusting screw out 4 turns.
  5. Apply a small amount of blue Loctite to the adjusting screw threads just above the disconnector tower. Loctite must be applied, as per Loctite instructions
  6. Turn the adjusting screw in 4 turns stopping when the mark on the adjusting screw and the noted point on the receiver line up.
  7. Recheck the trigger and most importantly recheck the safety engagement. If all checks are satisfactory, you are finished with the adjustment. If any of the checks are not satisfactory, clean off the Loctite as per Loctite instructions and start over at step 1.

 

INSTALLATION INSTRUCTIONS

M-K IIA3 Small Pin Models

DO NOT PROCEED UNTIL YOU HAVE READ AND UNDERSTAND ALL OF THE INSTRUCTIONS AND ARE A COMPETENT AND PROFESSIONAL GUNSMITH.

STM-M-KIIA3-0016-01

Supplement to TM-M-KIIA2-0015-02

Tuning of the M-K IIA3 adjustable overtravel trigger system

Safety

  • Read and follow all the safety tips and warnings found in TM-M-KIIA2-0015-02 before attempting to install the M-K IIA3 trigger system in a firearm.
  • You may request a printed copy by sending your request to:

The Wisconsin Trigger Company, INC.
W1332 Elmwood Ave, Unit B
Ixonia, WI 53036

  • If at any time you feel you have not installed the M-K-IIA3 properly stop and contact The Wisconsin Trigger Company, INC. immediately.

Help@WisconsinTrigger.com

INFO@WisconsinTrigger.com

Phone (920) 253-1516

FAX  (920) 262-3028

Installation

  1. Install the M-KIIA3 trigger housing and spring as per TM-M-KIIA2-0015-02
  2. Determine which side of the receiver you wish the safety switch to be on. The M-KIIA3 safety selector will install from the left or right side.
  3. Remove the screw holding the switch to the safety selector. Set the switch and screw aside for later use. See figure A. (below)
  4. Use a 1/16 Allen wrench to turn the locking set screw out 3 turns or until the overtravel adjusting screw turns freely. Then remove the Allen wrench. See figure B. (below)
  5. Install the M-KIIA3 safety selector with the overtravel adjusting screw installed flush with the rounded top of the safety selector. If the adjusting screw is protruding past the surface, the safety selector will not fit in the receiver. See figure C. (below)
  6. Install the pistol grip with the safety selector spring and detent. Install the hammer and spring as per TM-M-KIIA2-0015-02.
  7. Set the second stage by adjusting the disconnector as per TM-M-KIIA2-0015-02.

Videos of this can be found on The Wisconsin Trigger Company, INC. website at

http://www.wisconsintrigger.com/installation-instructions/

Overtravel

Overtravel is the distance the trigger will travel after the hammer has been released. With the M-KIIA3 system you can adjust this amount by turning the adjusting screw in the safety selector. When the screw is turned in you will decrease the overtravel and when it is turned out you will increase the overtravel. There is no preset number to look for, it is strictly up to the preference of the end user.

Keep in mind when adjusting the overtravel- the less overtravel, the crisper the stop of the trigger.  However, the trigger is less forgiving if quick follow up shots are required. With a greater amount of overtravel, the trigger stop will feel softer and the trigger will be more forgiving during a fast follow up shot. You do need some overtravel for the firearm to function properly. Insufficient overtravel will cause the hammer to bind and the firearm to malfunction.

The overtravel adjustment on the M-KIIA3 system can be readjusted without removing the fire control parts.

  • Adjusting overtravel

Properly verify your firearm is unloaded then recheck it before proceeding.

Only adjust the overtravel with the upper receiver removed from the lower receiver and no magazine in the lower receiver!! This will help ensure the firearm is unloaded and safe to work on.

  1. With the hammer cocked and a safety pad between the hammer and the receiver, pull the trigger to the start of second stage. Then slowly pull the trigger until the hammer is released and note the movement of the trigger after the release. This is your overtravel.
  2. With the hammer cocked turn the adjusting screw in (clockwise) to decrease overtravel. Turn the adjusting screw out (counterclockwise) to increase overtravel. If you adjust the screw in too far you will have zero overtravel and the trigger and hammer will not move freely causing a malfunction in the firearm.   Repeat this step until the desired overtravel is reached. With the desired overtravel set, lock the adjusting screw in place by turning the locking set screw inside the safety selector until it makes contact with the adjusting screw. Tighten the locking setscrew firmly to the adjusting screw. Do not overtighten as this will damage the adjusting screw and safety selector.  See figure B.
  3. Install the safety selector switch on the safety selector using the retaining screw you previously removed. See figure A.
  • Safety Check

Checking for proper safety engagement 

  1. With the hammer cocked, turn the safety selector to “Safe” and pull the trigger repeatedly. If the hammer does not release, pull the trigger and tap the side of the receiver while pushing and pulling on the hammer. If the hammer has still not released, pull the trigger back hard and hold it.  Check the hammer and trigger hook overlap. 0.020” is sufficient.  If the hammer has released during any of the checks OR you have less then 0.020” overlap start over with the installation. Go back to TM-M-KIIA2 0015-02 and follow the installation instructions. Please feel free to contact The Wisconsin Trigger Company, INC. at any time for help with your installation. We are more then happy to assist you. If the hammer did not release proceed to step 2.
  2. With the hammer cocked turn the safety selector to Fire and pull the trigger. If the hammer released and you have the desired overtravel return to TM-M-KIIA2-0015-02 to complete the installation and tuning of the M-KIIA3.

Illustrations:

click to enlarge