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Posted: 8/17/2013 7:16:44 PM EDT
A couple people have asked me for a rundown of what I’ve done to my Benelli M4. Here is a brief overview of the modifications performed to get it where I want it.
My M4 started out life in 2004 as an 11703 model. This was one of those lame models that had the four gas ports in the barrel. After about 8,000 rounds, the bolt carrier was deformed so much that the rails were swelled out and would bind in the rear of the receiver. Where the pistons contact the bolt carrier, the carrier was literally mushroomed out. I contacted Benelli, and they refurbished the entire weapon with an 11707 barrel, pistons, ARGO system, new bolt carrier and handguards. I then purchased a 3 position receiver extension and swapped it out so a collapsible stock would actually function. I then sourced a collapsible stock. I added a slew of carriercomp items to the weapon. I added a full length titanium magazine tube to reduce weight, a Wolff Spring spec'ed by carriercomp, top rail, 1/2" black titanium bolt handle, and a US made follower. From Freedom Fighter Tactical, I added a US made reproduction forearm, trigger, hammer and disconnector. These were for 922(r) compliance and provided a lighter trigger pull and a slightly smoother action from the coating on the hammer. I added a GG&G oversized bolt release. A DMW oversized safety button was added. The spring was lightened so engaging and disengaging the safety can be performed with one finger without breaking a firing grip. An Aimpoint T1 4moa dot on a LaRue low mount was added. I wanted QD sling mounts, so I modified a BLAM4 mount that replaces the front sling mount. I added an IWC QD mount to the bracket by drilling out an appropriate sized hole for the socket. I then had the assembly Cerakoted black to prevent rusting. 
The rear sling mount is from IWC, and is made for a Magpul MOE collapsible stock. It plugged right in to the established sling loop on the collapsible stock. The mount was positioned on the right side of the collapsible stock, this offered more freedom of movement with the sling and it was less likely to impede shouldering the weapon. 
I hated all of the weapon light mounting options. I tried them all it seems. They were either uncomfortable, required tools to disassemble the weapon or heavy. So I modified the FFT reproduction handguards to accept an IWC offset mount for a Surefire Scout light. This was a huge job that took me a lot of hours. After drilling out the mounting point, I back filled the area with epoxy. Then I sanded everything down so there were no rough edges. The handguards were then Cerakoted graphite black to mask the work area. For cosmetics, the inner grooves of the handguard were Cerakoted Burnt Bronze to match the rest of the weapon. 
After all this work, the weapon was refinished. After 12,000 rounds, it was pretty beat up. Rather than just a regular paint job, I opted to have the internal parts coated in Nickel Boron. This was a bigger job than expected since the entire weapon had to be fully disassembled. There were some areas of the barrel assembly that I could not remove such as the ejector. So the barrel assembly was simply painted Burnt Bronze. The chamber area was already chrome plated, so I wasn't too concerned. I fully disassembled the receiver, even the receiver extension, rear sight assembly, top rail, magazine tube, trigger group retaining pin and shell stop. The entire receiver was coated in nickel boron. A top coat of Burnt Bronze Cerakote was then applied to the visible exterior portions. 
The receiver extension was coated in Nickel Boron, and then the exterior was painted in Burnt Bronze Cerakote for cosmetics. This gave me a nice smooth Nickel Boron finish on the interior of the receiver extension. The plunger on the inside of the receiver extension was also coated in Nickel Boron. I had the shell stop completed coated in Nickel Boron as well. Since I am using the GG&G unit, the button itself bolts to the shell stop and covers up the nickel finish. 
I took apart the trigger group completely. The trigger frame itself was coated in Nickel Boron, and then the visible exterior portions were painted in Burnt Bronze. The shell elevator and the shell release lever were also coated in Nickel Boron. 
The pistons were coated in Nickel Boron. The bolt carrier was completely coated in Nickel Boron; I then had just the visible portion of the carrier painted in Graphite Black Cerakote. I didn't mess with the firing pin or the actual bolt itself. 
The aluminum portion of the collapsible stock was painted in Burnt Bronze Cerakote. The titanium magazine tube was painted in Burnt Bronze Cerakote. The carriercomp magazine follower was coated in Nickel Boron. 
When all the parts returned, I had some minor fitting issues from tolerance stacking. This lead me to polishing a significant portion of the weapon to bring the reliability back to 100%. The pistons were very tight, and shells were not ejecting with authority. I polished the following areas; Inside of the receiver around the magazine tube and up and down the receiver's rail raceways The shell stop The front face of the trigger group The shell elevator The breech latch The rails of the bolt carrier The bottom of the bolt carrier where it made contact with the hammer The receiver extension's plunger The magazine follower 
The pistons were polished until they fit freely into the barrel assembly 
Most internal springs were then replaced upon final assembly. In the end, everything worked flawlessly, but it was a lot of work getting there. 922(r) was not a concern since I had the following US made parts; 1.US Made Full Length Magazine Tube 2.US Made Follower 3.US Made Hammer 4.US Made Disconnector 5.US Made Trigger 6.US Made Forearm |
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Thanks guys. Most of it was a fun project. Some of it caused some hair pulling. Some of it was rewarding, since I can now tear apart the trigger pack in my sleep.
I've also amassed a huge pile of spare parts for the weapon. I recently snagged a complete trigger pack and a complete bolt carrier. A have a plastic divider boxes full of individual pins and springs. I forgot to add that I'm using a VCAS padded 2 point sling with QD connectors sewn in. The weapon has Meprolights night sights installed in the iron ghost ring sights. On the weapon light mount I made, there are two fasteners drilled through the plastic handguard from the inside of the handguard. They interface with two oval threaded flat nuts that were supplied by IWC. I countersunk the nuts into the handguard by grinding out a recess into the handguard. The excess thread was then sawed off. The entire work area was then filled with the resin epoxy. I then hand sanded the area to make the surface area smooth to the touch. This completely concealed the mounting hardware and gave a nice finished area for my thumb to rest. On the inside, I coated the bracket mount with resin epoxy as well. This "glued" the fasteners into the mount and prevents the screws from ever backing out. I couldn't tighten the screws super tight because it would cause the handguards to deform under the tension. So red locktite and the glue were required to make sure it never comes apart. Epoxy was also applied around the armature of the mount to give it a uniform one piece look. The epoxy also toughens it up some. I had to file the inside of the IWC mount significantly with a dremel to gain enough clearance around the ARGO plug and the magazine tube. There isn't a lot of room inside there to work. Given the curvature of the handguards, I have to shape the IWC mount in a vice with fine tuning hammer. This shaped the armature of the mount to align the weapon light with the barrel. 
Here is before I applied the resin epoxy to the outer portion of the forearm. 
Before I butchered it: 
Barrel Shadow 
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Almost huh? It's really not that hard of a job to disassemble assuming you have the right tools. A MAPP torch really helps with disassembly of the receiver extension and the magazine tube.
Today, I disassembled the carriercomp magazine tube and polished the entire inside of the mag tube. I took 0000 steel wool and wrapped it around a 12 gauge tornado brush in multiple layers until the fit was tight inside the magazine tube. I then applied 800 grit polishing media to the steel wool. I then put the rod in my electric drill and ran it for about 15 minutes up and down both ends of the magazine tube. I then cleaned all of the polish out, threw away the steel wool, and installed new steel wool with 1000 grit polishing media. I did this for another 15 minutes on both ends. The entire tube was then cleaned with hot soapy water to remove all traces of polishing media. The inside of the titanium tube is pretty much a mirror finish now. The polished inner tube creates less resistance against the spring. This is mainly a concern when the last round in the magazine is being ejected. Loading rounds is also a little easier. I do not recommend any lubricant inside the magazine tube. I found it causes the magazine to operate sluggishly and diminishes the shell ejection strength. You want these shells to be ejected onto the elevator with authority so they slide all the way to the rear of the elevator. |
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"Almost" only because I'm sure it would be an arm and a leg. So far I've installed the Benelli full length mag tub, the Benelli collapsible stock, Surefire forend, and new hammer, disconnector, follower, and trigger for 922r compliance.
I've followed the work you've done on your M4, and used your tutorial for swapping out the internal parts. Very cool stuff that even I could follow. |
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I hear ya. I think anyone could disassemble this weapon to the proper level if they needed to. Or, you could probably have a competent gunsmith disassemble it for you. I'd rather spend the money on the tools to do the job than on a gunsmith. Glad you liked the instructional posts on disassembling the different areas of the M4. I've been thinking about doing one where I completely strip and reassemble the trigger pack. It looks a lot more complicated than it really is.
I really tried to like the Surefire M80 forearm. I bought and sold two or three of them in the past in an attempt to like it. It was heavy, and felt like holding onto a pringles can. I tried a AFG, but hated that too. It seemed like a lot of weight and discomfort to simply add a weapon light. I tried the SideArmor rail, and found it to weigh as much as a boat anchor. I refused to use a mag/barrel clamp that prevented disassembly of the weapon. That set me on my path to make the low weight weapon mount that regained the excellent factory ergonomics of the handguard. |
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Thanks. I finished up the complete trigger group write up today. It was a lot more work than I expected to process all the photographs.
http://forum.benelliusa.com/showthread.php/32332-Benelli-M4-Complete-Trigger-Group-Assembly-Guide It's hosted over at the Benelli Forum. |
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Just noticed you did a tutorial on polishing the mag tube as well: http://forum.benelliusa.com/showthread.php/32317-Benelli-M4-Magazine-Tube-Polishing
Cool stuff! |
| Although I do love the way you attached the light. Pure genius! But couldn't you just screw in a section of rail and attached the light that way? Or isn't there enough room on the inside of the handguard to hold the screws? I am curious because I want to add a light to my M4 and I've been looking at my options. |
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Thanks guys.
You could screw a section of rail into the handguard, however there are some issues involved. The forward portion of the handguard angles inward and isn't parallel with the barrel. There isn't a lot of room on the inside of the handguard where you want the light mounted. You're basically limited to the area in front of the ARGO plug. I find that adding a rail section just adds another bulky part that will not feel nice to the hand. With a rail section, you also then have to add a picatinny rail mount to attach your light to. So I figured if I was going to do it, I might as well go all the way and mount the mount directly to the handguard. That was my reasoning at least. |
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Top notch build and write up..... 10/10
I'm getting ready to pickup the 922R parts and the trigger group work had me a little intimidated to be honest..... I was also planning to use a small piece of MOE rail and modify my US forend. I figured it would allow me to put an X300 and a Magpul RSA for when I want to attach my MS3 for 2 point operation. I hadn't mocked it up yet.... Am I way off base with my plan from your experience...?? How tough is the installation on the enlarged bolt release button ? |
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http://forums.benelliusa.com/showthread.php/32332-Benelli-M4-Complete-Trigger-Group-Assembly-Guide
This might help with your 922(r) trigger parts replacement. I did this tutorial to show the full disassembly of the trigger pack. Just take it as far as you need to to get the hammer, trigger and disconnector in. The job is really easy assuming you have the right tools. I show many proper tools and their use in the tutorial. If you don't have the tools, they are fairly inexpensive at Brownells. The shell stop is pretty easy assuming you have the right tools. Without them, it can be a real bitch. I have a write up on how to do it, but my photobucket account is overloaded this month. It should be back online by the 29th. http://forums.benelliusa.com/showthread.php/29534-Benelli-M4-Shell-Stop-Removal-amp-Install?highlight=Benelli+m4+she'll+stop You're going to run into some crowding issues with a MOE rail screwed to the handguard. Trying to get the tail of the light where you want it so you can activate it with your thumb is a pain. The tail of an x300 might not be very forgiving when using it during recoil. I'm thinking of switching to a non guarded button for this reason. An issue you may run into with screwing into the handguard is the handguards tend to flex as you apply tension on the fasteners. This prevented me from really snugging up my screws. So I red locktited the fasteners and epoxied over the entire assembly to prevent any movement or possible loosening. It also bonded my mount to the handguard completely. A side benefit was it was sand-able which allowed me to build up a smooth surface for my thumb to rest on. For the sling, I'd consider getting a BLAM4 mount, and modify if so that it is the RSA. You could drill out the bracket to make a loop for the MS3's hook. I build my QD mount for the front sling mount. |
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