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AR15 Armorer: Review/How-to: Clark Custom Guns Carbon Fiber Handguard & How to Vent

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Review/How-to: Clark Custom Guns Carbon Fiber Handguard & How to Vent

I decided to build another custom rifle and set my goals to build a very unique match AR. Weight is a factor in this build so I opted to use a Clark Custom Guns carbon fiber handguard. Similar to the rest of the parts in this build, I wanted to work with a company with reputable customer service, which produces or supports manufacturing here in the USA. This company has been around for over 60 years and continues to innovate like its founder James E. Clark Sr.

Free float handguard is the option to have these days if you are trying to achieve accuracy and stand out from the crowd. The Clark carbon fiber handguard offers those options and unlike most aluminum handguards, it is extremely light and versatile. Although Clark does not make the carbon fiber tube in house, they source it from a manufacturer in the USA. Carbon fiber is a desired material due to the high strength to weight ratio. Carbon fiber is extremely stiff with a high tensile strength, high temperature tolerance with low thermal expansion, corrosion resistance and lightweight properties. It is used in a vast variety of industries from Aerospace, Motor sports, Military applications and variety of engineering disciplines. With the high demand of Carbon fiber, naturally it is an expensive material. Carbon fiber is usually mixed with another material to form a composite. I won’t discuss all the different polymers or the processes, but I will get into details of this handguard. The Clark handguard is a carbon fiber reinforced polymer. The polymer used to make this handguard is an epoxy. Epoxy is widely used as structural glue in Aerospace applications and a matrix material which is reinforced by carbon fiber, it is however not the best polymer to deflect UV rays. While knowing the reinforcement and matrix of a composite is important, the manufacturing process is just as critical. The Clark handguard is made using the filament winding process. This process is popular for creating hollow core composites using carbon or glass fibers. A machine basically rolls fiber around a polymer on a mandrel or mold. Automation, software and machinery constitute a scalable process for mass producing precise complex components. The Clark handguard is made from 2x2 twill carbon fiber weave. This twill weave is much more popular than the standard 1x1 weave for aesthetic reasons. However, the reason why 2x2 weave is used for this handguard is due to the looser weave properties. Different variants of carbon weave have specific purposes, 1x1 is the common checkered flag weave which has the tightest weave properties and it is perfect for flat composite structures. While 2x2 and bigger twill patterns have a 3D diagonal presence with looser weave properties, which naturally have more give used for composite parts, which require bends and angles.

The Clark standard handguard is 12.7” long, has an internal diameter of 1.88”, outer diameter of 2.025” and thickness of 0.145”. It comes in three different lengths to suit your configuration. At only 6oz with the barrel nut, this is one of the lightest 12-13” handguards available. For my build with a match 16” barrel I opted for the standard size handguard. It is semi smooth with a matte finish and has been centerless ground, which explains the lack of excess epoxy resin on the outer surface. The wall thickness is ample to withstand a lot of abuse and be tapped for adding rails and other accessories. It comes with an aluminum backing plate with sling stud as an optional feature, which is terrific, other carbon fiber handguard manufacturers require additional fees/costs for this basic option. Clark grants the customer the option to send the tubes out with or without the sling stud hole. It is a complete handguard system with the exception of glue needed to mount the handguard to the supplied barrel nut. The barrel nut and bipod back plate is made from aircraft grade 6061 aluminum. Both are CNC from a block of aluminum, than turned on lathe and milled to spec on American made machines according to the manager of the local machine shop which Clark has been doing business with for over 30 years. The sling swivel stud and dome nut come from Uncle Mike’s, which I assume is made over sea’s, but I could be wrong since I have not confirmed the origin. The barrel nut and bipod back plate are not coated, left with their natural finish, while some may prefer a coating it actually worked out perfect uncoated for my build.

The Clark handguard will function perfect without any modifications, but there is ways to improve the mounting system. To mount this handguard you need to first tighten the barrel nut, it can be achieved by using a variety of tools such as a pipe wrench, strap wrench, adjustable spanner wrench or even an optional barrel nut wrench. I used a heavy-duty strap wrench to tighten the barrel nut, which left the surface free of any scratches or marks. I know for a fact, the barrel nut tool would not tighten any better than a good strap wrench, so save yourself the cash and use the tools you have on hand. When it comes to mounting the handguard to the barrel nut, it simply requires an adhesive glue/epoxy. Once the adhesive hardens you have completed the install. The result is a permanent bond between the handguard and barrel nut depending on the strength of the adhesive used. The downside is when you want to take the barrel nut off to swap barrels or other maintenance. However if you use a adhesive strong enough to bond the handguard to the barrel nut without causing a permanent bond like epoxy, I believe you should be able to free the handguard from the barrel nut without too much trouble.

The Clark handguard is already a great ready to go product, but I decided to put a unique twist on it for my build. I wanted to reduce the weight even more while functionally improving the mounting system and adding to the aesthetic with minor changes. Carbon fiber is heat tolerant and does not absorb heat as quickly as aluminum or polymer handguards, however it still gets warm during rapid-fire sessions. After performing heat tests on the Clark and M.I. aluminum handguard, I could have easily left the Clark as is, but there is always room for improvement so I decided to add additional ventilation. Keep in mind there is ventilation through the milled holes in the barrel nut and the open end of the tube already. This is where you can be as creative as you like depending on the tools you have at your disposal. Normally I would do this project using very expensive machinery which I have access to working in the Defense industry as an Engineer, but I wanted to use basic tools to showcase anyone at home can achieve the same results if you put the time and effort in. I highly suggest if you plan to follow through you get yourself a good respirator and perform this in a well-ventilated area. You do not want to breathe in carbon fiber dust, it is just as bad as asbestos and once it enters your lungs, it does not come out. If you want to learn more about the hazards, read a MSDS on carbon fiber. My setup included my shop vacuum and a mister bottle to help keep the dust to a minimum. I borrowed a brand new drill press, which can be purchased at most hardware store for under $100. Hindsight I should have used a higher quality industrial drill press because there was a little play on the chuck arbor. So I decided to go with 1/2” vent holes which would be easily achievable with any drill press. After taking extensive measurements of the tube and masking the entire tube with blue painters’ tape, I laid my template over the handguard and began marking the tube all over. This took quite a bit of time because accurately marking the tube with a ruler and other measurement tools is critical for a professional finish. I used an automatic center punch to go over approximately all sixty holes. When drilling through carbon fiber, you want to use a sharp bit at high speed to avoid fraying and other problems. Ideally a coated reamer, tungsten/diamond coated bit, or piloted cutters are used in the Aerospace industry, but these are not cheap or readily available at most hardware stores. Another important fact to remember when drilling through carbon fiber is the tip of the drill bit tends to move a few mm as it gets pulled by the weave sometimes once you have drilled through the polymer layer. It is more of an issue when drilling by hand or equipment, which has some play in the drilling mechanism. I mention this because unless you are using precision machines to cut the holes with expensive bits you might be surprised of the outcome if you are not careful and don’t pay attention. It is hard enough to drill through a flat piece of carbon fiber, the difficulty is amplified drilling through a round tube.

With the aid of the center punch index marks, I drilled small pilot holes than used a new Unibit step drill bit to enlarge the holes to 1/2”. When it was all said and done, I had half a day into this phase alone doing it without any help. I was very careful to keep the surface clean while keeping the drilling surface wet by constantly spraying as I was enlarging each hole to keep the carbon dust to a minimum while the vacuum was sucking away the shavings. I also cleaned the interior of the tube after each hole. Once I was done with all the holes I peeled away the blue painters’ tape I found myself with a mess of frayed 1/2” holes. This was expected, but I was also surprised how bad it looked, so I took my Dremel with a grinding bit and set it to 20k rpm, I carefully and lightly touched up every hole by moving the bit in a circular pattern. I followed that up with some 1500-2000 grit wet sanding and the end result was a complete vented Clark handguard. I took it a step further to mount a Midwest Industries aluminum end cap to give it a complete finish. The M.I. end cap is slightly smaller than the inner diameter of the Clark tube, so drilling the holes and keeping it centered as you tighten down each bolt can take some patience but it is possible. I also decided to coat the tube with a clear coat to protect it from UV rays as well as sealing all the holes I drilled to prevent any possible future fraying, which is not a concern, but added insurance. The gloss finish is your preference, you can easily just keep it matte if you did a good job of cleaning all the holes with the Dremel. From experience, trying to clear coat the handguard, I noticed like most carbon fiber composite products it is porous which explains the fish eye effect in some areas. Not happy with the results, I had a professional painter use the most expensive clear he had on hand. He confirmed no matter how many coats he put on, there would still be minor flaws simply due to the porosity of carbon fiber. Of course the more coats he put on the heavier it became and at one point he had so much clear on it the weight doubled from what I originally gave him, he stripped it all down and put a light coat to protect it from UV rays and give it a nice glossy finish but there is still a few fish eyes if you look for them. So do not be surprised if you do not get a perfect smooth finish with this tube. Once I got the tube back I polished it up with NXT and set to design a new mounting solution. After some testing and measuring, I came up with the idea to use a screw & nut combination with a tapered style compression setup. I took a small hex machine screw nut and grinded it down till I was able to slide it into one of the milled holes of the barrel nut. I measured 1/4” from the end of the handguard and marked the spot with an automatic center punch, same procedure on the barrel nut. I carefully drilled a small hole in the handgurad, than the barrel nut, cautiously avoiding drilling too deep. You only need to drill through the outer surface of the barrel nut. There is just not enough material to tap the inner portion of the barrel nut without disrupting the barrel threads. I added some blue thread locker to the machine screw and tightened the handguard against the barrel nut, it was solid and I was pleased with the results. However, I took it a step further to alleviate all the pressure from the single point of failure between the handguard and barrel nut. At this point you have the option to leave it alone, duplicate the same procedure on the top or sides, or use a pressure solution to strengthen it up. To keep it clean I cut a small 2mm x 1/2" strip of 3M double-sided sticky tape and stretched it around the barrel nut machined slot closest to the threads. If you look at the barrel nut there are two machined slots about 0.5mm deep all the way around the nut. You can also use an o-ring but finding the exact size and thickness will be challenging and will not give you the same result as 3M sticky tape, which is versatile and really strong. You will have to experiment with different tape thickness, when I had it just right, it required quite a bit of force to slide the handguard on the barrel nut for a tight seal between the two without having a permanent bond. Between the 3M compression fit and screw/nut combination, I had a bond tough as epoxy, but not permanent which would allow me to take it off in the future without too much hassle. Additionally if you want to add accessories you can easily add a picatinny rail by drilling and tapping this handguard, due to the thickness, a couple machine screws will do the trick supporting the rail, for added insurance some adhesive can also be used.

When it comes to bang for the buck, you can not beat the Clark Custom Guns carbon fiber handguard. It is one of the highest quality and lightest carbon fiber handguards available. The price point alone is worth a second look, for such a high quality product you would expect to pay much more. It is a perfect blank slate to let your imagination run wild to design your own vented handguard. With three different length options, this handguard can suit any of your rifles and configurations. The fit and finish are consistent with high quality composite products produced here in the USA and the customer service is fantastic which speaks volumes in this industry. I would not hesitate to recommend this handguard to anyone.

Video: How to install Clark Carbon Fiber Handguard:


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    11/03/2012 06:42 PM


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