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Benelli M4 -- Sidearmor Rail Review


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I received my Sidearmor rail in the mail today. This rail system has generally been given a thumbs down in the past mainly due to the out of spec Picatinny rail system.


I saw value in the system due to the retention of the factory handguards and the ability to mount the weapon light parallel with the barrel. This keeps the weapon light out of the vicinity of your hands on the handguard. A velcroed tape switch to the factory handguard would work great. A properly placed light with a momentary rear cap could be activated via your thumb.


The top rail is closer to picatinny spec than the factory unit. The raised locators are thicker, and part of the center cut is left in tack. While it isn't true spec as being a solid locator, it is better. Without getting too technical, there is more meat on the rails than on the factory one.


In the current configuration, a true spec picatinny rail could not be used on the Sidearmor rail because it would obstruct the iron sight view. The rail sits slightly higher than the factory one. I attempted to use a ladder rail from Surefire, but it completely blocked the view. It sits up higher because the rail itself is sitting on top of a base that conforms to the top of the receiver. This wider base adds lateral stability to the rail.


The Sidearmor rail is attached with five hexhead screws. It also does away with the washers like the factory unit has.

At the front, there is a barrel clamp that indexes and attaches just ahead of the handguards where the barrel casting supports the magazine tube. Once the barrel clamp is installed, the top rail aligns with the clamp and has a captive spring loaded knob that links the barrel and the top rail together. This offers much needed support to the front of the rail. No tools are needed to disassemble and clean the weapon.


The side rails are proprietary to the Sidearmor top rail. The top unit has a dove tail that their shell carrier and side rails engage. Then they are screwed into place. Sidearmor offers two different size side rails. The rail comes with a long rail. I purchased a small rail for my light. I may purchase a small to replace the longer one for my sling mount to reduce weight and bulk.


I decided to give their shell carrier a try. I have tried the Tacstar and the Mesa unit in the past. This one is by far the better of the set. It uses a spring loaded detent to retain the shell in place. It is also easy to remove. Two bolts, and it comes off. It only holds four rounds, so it is relatively light weight. I had no issues carrying the weapon slung on a brass hunt I went on earlier today.


Mounting my front sling mount to this rail was better than on the Surefire M80 rail. The rifle seems to hang a little better being higher up. It also keeps the sling away from the handguard. The sling is out of the way of the shell carrier also.


Kip's Picatinny rail is a much more solid rail. If you're primary purpose is mounting an optic with a rock solid mount, his is the way to go.



Sidearmor claims that the rail weighs around 11 ounces with one full length side rail installed. They didn't mention that you are removing 1.5 ounces by removing the factory top rail. The small side rail I added is around 1 ounce. The shell carrier is approximately 4 ounces.

A stock Benelli M4 weighs approximately 8.5 pounds unloaded. Mine, fully loaded weighs around 11 pounds. 12 gauge rounds weigh quite a bit of it. There are 12 rounds in/on the weapon.


Overall, I'm happier with the rail than I had expected. A lot more thought went into it than you can see from their webpage. They performed a lot of lightening cuts on the underside of the rail.




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OK, maybe it's me but....


What would be the reason for this?


Scout optics forward on the bbl? Kind of useless on an entry weapon


Lights hung off the sides? Balance is thrown off


Laser sighting? Best applied to the bottom in line with the bore


All that said, Mesa with extra rds does the trick with a Surefire frontend.


Or just switch out to Kip's rail and a H1 / T1 sight.





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With the Surefire M80, the side rail is right where your hand should be. I had one. I sent it back. There are no reliability issues either. It's been mentioned many times that the M80 has caused binding on the gas pistons. This setup uses the factory handguards which are far more comfortable than the M80 rail system. I tried several types of rail covers and ladder rail covers. It was okay, but not great.


The Mesa shell carrier does not have the forward brace. So any and all leverage applied to the shell carrier is taken by the five scews mounted in the aluminum receiver.

I hated how the shells were inserted into the Mesa carrier. They took two hands to insert the shells. I modified the rubber tube to reduce the tension. The detent design of the Sidearmor is much easier to actually use.


The Surefire Scout Light is a weapon light. It weighs 7 ounces or so with a Larue mount. If that throws my balance off, I must have an inner ear problem. The whole point of the design is to keep the weapon light away from the handguard so it doesn't obstruct your grip. If you use a momentary tail cap, you can press it with your support hand thumb. When not using the light, it is out of the way. Or you could run a tape switch to the factory handguard with some velcro.


I have no intention to mount a laser, and probably no optic either. Kip's rail is much better quality. It is as tough as the 5 screws holding it to the receiver will allow it to be. The Sidearmor has a wider foot print on the top of the receiver. So any torsional twisting of the rail is met with a larger base. The rail covers from the ejection port all the way to the opposite side to a similar height. The front rail mount to the barrel provides even greater amounts of stability.


My next step is to drill some holes to accept some zip ties to secure my tape switch wire. Then we get to see if the 18" wire will work, or if I have to use the 40" (thanks Surefire for not making inbetween lengths).


I took some better photos along with comparison shots between the factory and Sidearmor rail. I'll post them later tonight from home.





Edited by StrangerDanger
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If someone is complaining about gas discharge, then plain and simple, they do not own one, nor have they ever fired one. The Mesa carrier, and the rail would be a lot better if they had the solid block across the top. Brugger & Thomet did it to match the factory rail, Benelli and Mesa have no excuse. Specs are avalible at Surefire for the M900A, with the turbo head (KT4-HA) option. All I can say is that it is bright.

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I like that one too! One of these rail systems is definitely in my M4's future. Will start researching these after I get the mag tube squared away.


Here's a review I did on the KZ with some pics starting on page 3




Here are some more Sidearmor pics too








Hookster :)

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i just wonder why the botac system doesn't feature full spec picatinny rails?


It actually does have the 1913 rails. Here's the link to the description and pictures on the website.




I bought this one and the Surefire M80. I returned the Surefire and kept the KZ forend. I just liked the fact that its all metal and feels really sturdy. Also it didn't hurt that its made in the U.S. and that it was cheaper than the Surefire forend.

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