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StrangerDanger

Benelli M4 -- Complete Trigger Group Assembly Guide

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Recently, I’ve had a few requests to do a disassembly/reassembly guide for the trigger pack of the Benelli M4. Today I had some spare time to kill, so I decided to try to tackle it. This manual can be used as a guide for pretty much any Benelli shotgun out there.

 

Not everyone needs to do a full disassembly. They may be doing 922® upgrades or simply changing out their safety button. Perhaps you want to have your carrier welded up? You can jump around through the photographs and see what is needed to get the assembly apart to do your job.

 

In this tutorial, many of the images will have lines on them indicating what you cannot see inside of the parts. I used the color blue to indicate the position of the tools such as punches. I used green to indicate the position of the roll pin or other type of assembly pins. White and black indicate the general assembly.

 

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Note: The trigger pack I am using is a spare complete trigger pack with a Geisselle hammer installed.

 

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The Tools

Before proceeding into this tutorial, I would advise that you have some proper gunsmith grade tools. You do not need hundreds of dollars’ worth of tools, but you do need the basics to prevent marring your work. Proper tools will also keep the swearing to a minimum. This job we’re about to perform will cause some swearing. You will be required to manipulate many small spring loaded pieces that must be aligned perfectly. It might be pretty miserable to perform if you have big sausage fingers. Take this under advisement before you’re forced to make the walk of shame to the local gunsmith with a shoe box full of parts. Naturally, if you get stuck somewhere, get a hold of me and I’ll help you in any way that I can. If you’re still stuck or have broken something, you can send the assembly to me to repair. All I will charge is the cost of shipping it back and the cost of any needed parts.

 

The same applies if you want something repaired or if you want 922® compliance parts installed and do not feel you can complete the task. I’ve done many installs for locals and other members on this forum in the past. If I have the parts on hand or you are sending them with the item, I usually have the work back in the mail to you the next morning.

 

1/16 Punch

3/32 Punch

Snap Ring Pliers

Dental Pick

Alignment Tools

Assembly Block

Brass Hammer

Rawhide Mallet

Edited by StrangerDanger

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Disassembly of the Trigger Assembly

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The first step to disassembly of the trigger pack is to remove the Trigger Pin Spring (also known as a snap ring) from the left side of the trigger assembly. To do this, you need a pair of snap ring pliers with an appropriate size pin size. I believe it is best to use the .050” diameter pins. Apply pressure with the snap ring pliers so that the snap ring expands and allows you to remove it from the Trigger Pin Bushing.

 

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Note the grooves along the side of the Trigger Pin Bushing. These grooves are what the snap ring seats into. You must align these grooves up when reassembling or you risk damaging the Trigger Pin Bushing by allowing the snap ring to squeeze the bushing incorrectly.

Edited by StrangerDanger

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Now with the snap ring removed, you may push the Trigger Pin Bushing out from left to right. Be sure the hammer is decocked before doing this. Since we’re doing a full disassembly, push the Trigger Pin Bushing completely out with a punch or an alignment pin. As you push the Trigger Pin Bushing out, the Shell Release Button will likely unhook from the top of the Hammer Spring Cap as shown in my photograph above.

 

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As you pull the Trigger Pin Bushing out, be careful not to dislodge the Shell Release Lever yet. There is a small spring attached to it that is easy to damage.

Edited by StrangerDanger

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Here, the Trigger Pin Bushing has been removed. The Trigger Pin Bushing acts as an alignment pin that holds the Carrier, Shell Release Lever and Hammer to the Trigger Guard. So once the Trigger Pin Bushing is pulled out, everything will start to fall apart if you like it or not. Once the Carrier pulls away from the Trigger Guard, the Carrier Plunger/Carrier Spring will simply fall out of the Breech Latch. The Shell Release Lever will still be retained to the Trigger Guard by the Shell Release Spring that can be seen along the top of the Shell Release. Pull the Hammer, Hammer Spring Cap and Hammer Spring out of the Trigger Guard and set them aside.

 

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Here is a close up of the Carrier, the Breech Latch and the Breech Latch Pin. To disassemble this part, simply tip the Carrier over and the Breech Latch Pin will fall out. The Breech Latch will then simply pull away from the Carrier.

Edited by StrangerDanger

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Here you can see how the Breech Latch Pin comes apart.

 

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Here you can see the Carrier Plunger and the Carrier Spring. The spring simply slides over the plunger.

Edited by StrangerDanger

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Here is the Hammer, Hammer Spring and Hammer Spring Cap pulled free from the Trigger Guard Assembly. Note the hole in the Hammer. This is what the Trigger Pin Bushing inserts thru.

 

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Here the Shell Release Lever has been pulled off of the Trigger Guard. Try not to bend the Shell Release Lever Spring when you separate the parts.

Edited by StrangerDanger

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Trigger Disassembly

 

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Here we are going to remove the front Trigger Pin. This pin also retains the Shell Release Lever Spring. Tap out the pin with an appropriate size punch and hammer from either side.

 

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As you tap the punch thru the assembly, the punch will act as a slave pin and hold the Trigger to the Trigger Guard Assembly.

Edited by StrangerDanger

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Here the Front Trigger Pin has been removed and the Trigger Assembly has been pulled out of the Trigger Guard. The Shell Release Lever is free and can be removed now.

 

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Here is the Trigger Assembly removed from the Trigger Guard.

Edited by StrangerDanger

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Here we are removing the Rear Trigger Pin. There isn’t really much purpose to removing this pin unless you’re doing a complete tear down for some reason. This pin does not need to be removed in order to pull out the Trigger Assembly. You will notice that the Trigger Pin taps out quite easily.

 

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Edited by StrangerDanger

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Here we are disassembling the Trigger Assembly. Use a 1/16" punch to tap out the Disconnector Pin.

 

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Here the Disconnector Pin has been removed. The Disconnector, the Disconnector Plunger and the Disconnector Spring now can be pulled out of the Trigger.

Edited by StrangerDanger

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Here is a Diagram of the Trigger Assembly.

 

 

 

Safety Disassembly

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We are now moving on to the manual safety in the Trigger Group. Use a 3/32" punch to tape the Safety Plunger Retaining Pin out from either side.

Edited by StrangerDanger

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As you tap the punch thru, it will act as an alignment tool that retains the Safety Plunger and Safety Plunger Spring.

 

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Here all the parts of the Safety have been pulled out.

Edited by StrangerDanger

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Here is how the Safety works inside the Trigger Guard. The plunger presses against the Safety Button. The tension is set by the spring. If you would like a lighter safety, clip a coil or two from the spring. You do not want a safety that is too light to press. I found the factory tension to be a little too much for me. I cut about two coils off so that I could manipulate my DMW oversized safety button (not shown in these photographs) with the second knuckle of my trigger finger.

 

If you are left handed, you can reverse the operation of the safety by simply inserting the Safety Button from the left side of the Trigger Guard.

 

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If you’ve made it this far, you now have a completely stripped Trigger Guard.

Edited by StrangerDanger

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Reassembly Process

 

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Insert your Safety Button into the Trigger Guard. Insert it from the left side of the Trigger Guard if you are left handed.

 

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Apply some grease to the Safety Plunger before reassembling.

Edited by StrangerDanger

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Insert the Safety Plunger into the Trigger Guard.

 

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Insert the Safety Plunger Spring on top of the Safety Plunger and push it down until both parts bottom out against the Safety Button. You can feel that without spring tension on the Safety Plunger, the Safety Button will move unimpeded.

Edited by StrangerDanger

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This image overlay shows exactly what you are doing with the Safety Plunger Spring and the Safety Plunger. You must compress the Safety Plunger Spring while you tap the Safety Plunger Pin into place. If you do not compress the spring, you will damage the Safety Plunger Spring when the Safety Plunger Pin drives into the side of it. There are various ways to accomplish this. I found this Magna-tip from Brownells works the best to compress the spring and allow me to tap the pin in. If you do not have this particular bit, you can try to use a small punch or dental picks to keep the spring compressed while you hammer the pin into place. Expect to swear a little here. It’s a pain in the ass.

Link to Brownells: 080-431WB

S&W Rear Sight Spanner (2 per pak)

 

 

 

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It is hard to see the top of the Safety Plunger Spring in this picture. You must keep the spring compressed while drifting the pin into place or you’ll be buying a new spring.

Edited by StrangerDanger

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Once the Safety Plunger Spring is retained under the pin, you can hammer the Safety Plunger Pin the rest of the way in. I really like these Brownell’s Roll Pin Starters. The nipple on the bottom keeps the punch from slipping off the pin.

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/punches/roll-pin-starter-punches-prod20640.aspx

 

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Here the Safety Plunger Pin is flush with the Trigger Guard.

Edited by StrangerDanger

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Without the Trigger Assembly in the Trigger Guard, you can see how the Safety Plunger interacts with the Safety Button. When you push the safety on and off, you are Safety Plunger is forced into the raised edge of the Safety. This causes the Safety Plunger to compress against the Safety Spring.

 

Trigger Assembly Reassembly

 

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Now we are moving on to reassembling the Trigger Group. Here the Disconnector Spring and Disconnector Plunger have been inserted into the Trigger. Apply some grease around the base of the Disconnector Plunger.

Edited by StrangerDanger

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The Disconnector is then seated into the Trigger Assembly loosely.

 

Side note: Note the hook like features on the right side of the Disconnector and on the right side of the Trigger. These hooks (or sears) are what engage the hooks on the Hammer. As the bolt cycles to the rear, the Hammer pivots back. The Hammer's hook presses against the top of the Disconnector. The Disconnector then compresses against the Disconnector Spring and Disconnector Plunger. This rocks the Disconnector to the rear and allows the Hammer's hook to slip past the Disconnector. If the Trigger is still being pulled to the rear, the Hammer Hook will engage the Disconnector's sear. If the Trigger has been released, the Hammer will disconnect from the Disconnector's sear and be caught by the sear on the front of the Trigger.

 

To help visualize what is happening, make sure your M4 is empty. Cycle the bolt to ensure the hammer is cocked. Press the trigger and hold it to the rear. Without letting off of the trigger, cycle the bolt and allow it to return to battery. This simulates a round has been fired. Cycling the bolt has recocked the hammer. Since you are still holding the trigger to the rear, the hammer hook is being held by the Disconnector's Sear. Now, let off on the trigger slowly and listen for the audible click noise. This sound is the hammer hook disconnecting from the Disconnector and engaging the Trigger Sear. The weapon can now be fired again by pressing the trigger.

 

Some may be wondering what the purpose of the Disconnector is. If the Disconnector was not present on the M4, the hammer would fall forward and ride the bolt carrier into battery if the trigger was still held to the rear when the bolt cocks the hammer. The M4 would not go full auto without the Disconnector. The hammer is faster than the bolt, so you'd simply end up with a live round in the chamber, and the hammer decocked. Needless to say, you would not be happy.

 

I recommend taking your trigger pack out, and manipulate the hammer. Observe how it makes contact with the Disconnector and Trigger sears. Cock the Hammer with the trigger pulled to the rear and with the trigger in its rest position.

 

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Using a 1/16" punch as an alignment tool helps to align the Disconnector with the Trigger.

Edited by StrangerDanger

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You cannot see it, but the punch is still partially in the Trigger Assembly holding the Disconnector in place. Manipulating the Disconnector Pin is very hard since it is so small. Fortunately, the fit into the trigger isn’t very tight. You can press the pin in with finger pressure only. The trick is to get the hole aligned while they’re under spring tension.

 

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When viewing the hole from the opposite side you have the Disconnector Pin started in, you can visually align the holes as you press it the rest of the way in.

Edited by StrangerDanger

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Here the Trigger Assembly is assembled. The Trigger Spring simply presses into the hole at the base of the trigger.

 

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Tap the Rear Trigger Pin into the Trigger Guard.

Edited by StrangerDanger

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Make sure the Trigger Pin is flush with the Trigger Guard.

 

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This view shows you how the Rear Trigger Pin engages the back side of the Trigger. The Rear Trigger Pin acts as an overtravel and pretravel stop for the Trigger.

Edited by StrangerDanger

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