stevenb

I've read about several people having the issue where the bolt is sticking to the rear during cycling. I'm currently running into this same problem. However it has been an ongoing problem and I've had probably 5000 rounds thru the weapon. You can make it stick to the rear simply by pulling the bolt to the rear (not the bolt lock) Under close examination of the bolt carrier, I may have found the problem. Where the gas pistons impact against the bolt carrier, it appears that the metal has began to deform from the impacts. I then realized that this portion of the bolt carrier is the rail in which it rides within the receiver. I think the rails have expanded due to deformation and are binding in the receiver. If you look at the outer edge of the bolt carrier rail, you can see where the finish has prematurely worn off around the front end. Pulling the bolt to the rear, you can feel the bolt binding. Even with the bolt carrier tail out of the recoil spring assembly (remove the trigger group and pull the tail downward while inserting the bolt carrier group into the receiver.) I have one of the 4 gas port barrels. I had originally broke one of the gas pistons within the first 50 rounds of owning this weapon. Now, as soon as I have some time, I'm going to call and return it to Benelli. Hopefully they'll replace the entire weapon since those swelled out rails have worn the inside of the receiver rails. Honestly, the design is pretty poor for the impact site for the gas pistons. To ensure that it wasn't something else, I removed the top rail completely to prevent any type of binding. I also removed the bolt release. No tacstar side saddles were on the weapon either. The weapon couldn't be any cleaner.

Mitch, Really glad to see this project moving along. I think people will be real pleased with the hanguard/top rail interlock method. I would imagine the design to be copied in other rail systems in the future... Any new weight measurements for the assembly? Or significant changes to the forward barrel extension engagement? For reference, I'd weigh the OEM handguards and the top rail and fasteners. The real test will be the ergonomics of the handguard assembly and the weight of the unit. Steve

Sure, I'm testing on my weapon a portion of the rail assembly. I'm using an extended top rail that is unsupported. This keeps the weight of the system down and uses the factory handguards. The unit also mounts the Mesa Tactical shell carrier. Far superior to any other carrier I've used. I trashed the Tacstar POS. Currently, I am still using the Side Armor barrel clamp picatinny mount for my sling and laser assembly. The quick detach sling mount is distributed by Sidearmor as well. The optic is a EOTech 552 holographic scope. The length of the rail allows me to properly mount it on the Benelli. I'm fielding a 12mw Aimshot visible green laser mounted in two ARMS 22 low mount scope rings. I modified the factory handguards to accept the tape switch for the laser device. The sling is a 3 point sling from Specter gear. I have an oversized bolt release and charging handle from GG&G installed also. The biggest hurdle for the FCAM system is to keep the weapons weight down. The M4 is already a heavy *******. Far heavier then a M1. Giving the ability to hang other heavy objects on a weapon can cause problems in itself. The next issue is ergonomics of the system. I really like what I'm using at the moment since it uses the factory handguards which are top notch IMO. The weights Mesa has shown me is very impressive and I hope to put one of their systems on my M4 when available. -Steve

Very nice! Good price too! -Steve

Funny! Reminds me of that Surefire picture. I'm actually weighing a light mount option. Not exactly sure which way I am going to go with it yet though. I'd like a gladius, but due to the layout, I think a tapeswitch option is going to be mandatory. I'm thinking under my middle/ring finger on my off hand. The best thing about Mesa Tactical is they have the ONLY useable shell carrier. The Tacstar is a POS. It caused way too many problems. -Steve

Hey guys. I modified another project I am working on (Mesa Tactical FCAM for the Benelli M4) to be something simpler for those without the need of a 4 point rail system. Plus, the rail uses the factory handguard. This item simply replaces the top factory rail on the Benelli M4. As you can see from the pictures, it offers a shell holder also. The extended rail is perfect for the EOTech, I actually cut it so it would be an ideal fit. You'll notice that the cuts on the bottom are pretty rough due to my limited tooling on hand. I did most of the work with a file. The rail is extremely sturdy and has no flex that I can see. For more pictures, check out this link: http://www.citlink.net/~boehm/2005-09-11/ I shot it yesterday with the rail system installed. I have the 12mw visible green laser cowitnessed with the EOTech 552. The rail held a zero perfectly. I drilled holes into the factory handguard so I could ziptie the tapeswitch to the forearm. Very solid, and the wires routed out of the way very nicely on the Sidearmor forward rail mount. Let me know what you think. -Steve

STA, Mine sounds exactly like yours. Very little fouling is present on the front of the gas plugs. I have never disassembled the plugs themselves. I'm not even sure if it is possible without some specialized tools. My carrier knocks back with light taps as well. Generally the weight of the carrier unlocks the bolt and allows it to travel rearward. Generally, this is how I invision how the plugs work in the ARGO system. The pressure charge enters the ports against the pistons themselves. You'll notice the relief cuts are on the pistons. My guess is this is to prevent any overpressure and initial pulses. Fouling in general would likely take the easiest route out and that is along the pistons. My guess is that the "Auto Regulating" effects of the ARGO system only kick in if a preset dangerous pressure limit is met. Also remember that the ARGO system is self cleaning. It basically burns off the carbon fouling continuously. There are a couple other ideas I have about how it might work. I would really like to get some better technical information about the weapon. I should have bought that USMC field manual I saw on Ebay months ago. Overall, as easy as it is to cycle the action by hitting it on the ground should give you a clue as to how hard the pistons should be striking the surface of the bolt carrier. I've seen pictures of peoples bolt carrier deformed and they've bound up inside of the receiver. I sheared one gas piston in half myself 50 rounds after I bought my 11703 brand new. Was it a fluke? Who knows. I can tell you that the M4 functions with a single piston though, it runs slugish, but it does run. I only found out that it was broke by the broken section of piston becoming lodged betwen a shell and the shell elevator. You'll also notice that the pistons themselves do not move very far. They travel roughtly a 1/3 of an inch before bottoming out against the barrel relief cuts. All in all, I am giving a lot of trust in the Benelli design, and the knowledge that the Marine Corps. are using this weapon overseas as we speak. As hard as I am on my weapons, it doesn't scratch the surface of what those men are putting them through every day. I'm going to continue beating on mine, and if it breaks, Benelli will fix it. I'm not going to turn my combat shotgun into a safe queen. The thousands of hard rounds put through mine so far have not shown any wear and tear... Benelli went at the M4 to make it as simple as possible. That's why things like return springs were not included on the gas pistons to maintain them at a specific point. Sorry I cannot give specifics, just my own opinion. If you call Benelli, you'll get a different answer with every single different customer service rep. -Steve

1. You need the 11707 model in order to simply drop the collapsible stock onto the weapon. With some gunsmithing, any of the older models can accept it. I couldn't tell you honestly what the case is legally. 2. The M4 (there are two models, the 11703 and the 11707) has 4 barrel ports as well as a removeable choke. I've been beating on my 11703 for about a year now and have had very little trouble. I'm pushing close to 5000 rounds through it of assorted ammo including high base 3" shoulder buster slugs. I believe the arguement that the 4 port design is inferior is off base. I believe that the ARGO system regulates the proper gas pulse reguardless how much gas is dumped into the system. Reguardless of the load, the weapon is cycled exactly the same assuming the minimum preasure is met. The 4 port design scavanges more gas from the barrel to properly operate low recoil loads, and to lessen the initial gas pulse into the gas system. Most failures have been documented as metalurgical failures of parts. 3. Whole issue is up in the air and no one wants to deal with it. 4. Haven't even seen a good picture of the M80 rail system. However, the FCAM system from Mesa Tactical that I've helped work on is VERY promising. I have the prototype right now, and it does far more then any current rail system on the market. 5. Can't help you there. -Steve

Aj, Thanks for the comments. With the newest revisions, the system will work with the 14" entry barrel quite nicely. I'd love to get one myself and make a SBS. All the shell holders are optional, so the user can decide what they can deal with. I'm extremely pleased with the weight of the assembly. Every time we turn around we find another way to lighten the unit without compromising the stability/strength of the system. We recently came up with some ideas for the actual rails that people will wonder why no one ever did it before. -Steve

Red Cobra, Where'd you buy that HK in the other thread? Given the general pricing of other rail systems on the market for the M4, I feel this system will compete strongly considering what you get. No pricing has been finalized since we haven't finished the design yet. -Steve

That same rail can be moved back to any of the mounting holes. Also, shorter lengths will be offered as well. I really think this is going to be the general design for the length. I'm leaning towards the weight savings over the support. -Steve

Again, if anyone sees something they don't like, please explain your points. We're weighing any and all ideas. I agree that the top rail doesn't need to be any longer then the handguard. If someone can think of a device that needs to be mounted that far up, please indicate what. Given the iron sights on the Benelli, no extreme forward iron sights are needed. The only real reason the rail was extended so far out in the beginning was to simply support the side rails. In this current design with the short top rail, side rails can be mounted as such: The only concern then is having an unsupported rail extending past the handguard. This leaves any device mounted this far forward subject to more damage since it is less protected. Any comments/concerns about the design on how the handguard attaches to the top rail? The stand off bits are round, so you don't need to index them as if they were a hexhead shape to the rail. The rail groove is conformed to the shape of the bit. The number of these interlocking engagements is subject to change. Put it this way though, this design locks up my plastic prototype handguard rock solid. The same holes in which the screw threads into the standoff is the same one in which the side rails are mounted to. So none of those holes will be exposed allowing any gases to vent. We were considering using the gas piston body to add extra strength to the handguard portion. You can see this groove in the photo above showing the inside of the handguard assembly. This groove seated up against the gas piston assembly within the M4. During my trials shown above with the boat, thermal transfer issues became a problem. Also this design complicated proper indexing of the handguard. Too much stuff needed to be aligned inside the handguard to get a proper fit. So it was scrapped. Different length picatinny rails will be offered, so you don't need to add unneeded weight or add unused rail space that can hang up in your gear. The bottom rail will be optional much like the sides. For those of you worried about removing the factory picatinny rail, I can tell you it was extremely easy to do. Very little effort was needed to break loose the 5 screws on the top of the receiver. These flat head screws will be replaced with quality torx bit screws. Also, there is a rubber gasket installed on the inner side of the top rail where contact is made with the receiver on the side under the shell holder mounting plate. This gasket will protect your firearms finish. If I remember correctly, it measures aprox. .03", so the plate is not held very far off of the receiver. Our goal weight for the project is under a pound. Right now we are under this weight when measuring the top rail, handguard assembly and the polymer handguard. Hardware and rails not taken into account nor the shell holders. This also doesn't calculate the weight that has been removed from the weapon to install this unit. You loose the factory handguards, receiver picatinny rail and mounting hardware. So you're not simply adding a pound of dead weight. Also, this weight isn't hanging ahead of the handguards which works against you using leverage, the mass is behind the handguard assembly along with the majority of any items you add. Our next phase will be to test durability of the assembly. It's an interesting balance between durability/ridgidity and weight. -Steve

Here are some further pictures of the engagement of the rail system between the handguard assembly and the top rail. http://www.citlink.net/~boehm/prototype13b.jpg http://www.citlink.net/~boehm/prototype14b.jpg Here are some fully assembled shots: -Steve

This project is still going strong. I recently took possession of a prototype top rail section. The designs are changing faster then we can keep up with as we refine the final design. First, the maker has decided to go public with this project. This will be a product developed and produced by Mesa Tactical. You can find more information about their products here: http://www.mesatactical.com/ Currently, this Benelli M4 project is called, "Floating Combat Accessory Mount, or FCAM system." Here is the prototype that I have in my hands (EOTech 552 mounted): http://www.citlink.net/~boehm/prototype08b.jpg http://www.citlink.net/~boehm/prototype07b.jpg http://www.citlink.net/~boehm/prototype06b.jpg With the high number of revisions done to each segment, we've significantly reduced the weight of the unit. Final numbers aren't out yet though. I won't guess at a final weight yet since strength issues have to be determined. This is a current render of the target goal. We've yet to decide if we want to extend the rail past the end of the handguard further. The key issue is weight. Now for how the unit assembles. Notice on the image above the number of holes on the pink "handguard Assembly." The 5 larger holes shown offer a binding post to be mounted on the inside of the handguard. These 5 holes also serve as the placement for picatinny mounted rails. There are identical holes situated on the other side of the handguard assembly. The "Top Rail Assembly" that is rendered in light green has slots milled into it that accept the binding posts mounted on the handguard assembly. These posts lift up into the top rail assembly, then slide to the rear aprox. a quarter to half an inch. The handguard assembly at that time seats against the receiver extension which the factory handguards mount to. This is a simple fludic motion that allows you to lift the handguard assembly up into place, then back to lock into the top rail before the barrel is seated. Once the barrel is seated against the front of the handguard assembly, the barrel extensions interface with the front of the handguard assembly and lock the rail into position. Here is the disassembly process: Here's how I would caption the steps showing how to field-strip a weapon with the FCAM installed: 1: Remove the magazine cap. 2-3: Remove the barrel. It slides through the FCAM assembly and off the weapon. 4-5: Remove the FCAM forend. Push the forend forward and then down and it slides off the FCAM top rail. Note that any forward shell holders, side rails or ventral rail are attached to the FCAM forend and are removed with this step. 6: Now the bolt and trigger group can be removed to completely field strip the weapon. The FCAM top rail remains attached to the receiver. -------------------------------- The small holes on the handguard assembly offer the user the option to mount Mesa Tacticals shell holder also. This is a similar unit as the one shown on the left side receiver. More to come. -Steve

STA, Excellent job with the pictures and the legwork. I tried to photograph those ports before and couldn't do it. I feed my Benelli whatever I have and don't worry about it. If it breaks, Benelli gets to buy me a new one. I have 3000 rounds of 3 dram birdshot through it without any problem. Since then I've fed it many high power slugs. No wear can be seen on the carrier. I honestly believe that the gas piston I broke in under the first 50 rounds was a material flaw. Again, if it breaks, Benelli will buy me a new shotgun. Since their documentation with the weapon says nothing about limiting any particular barrel with a specific load type. -Steve