The GnZ AR15 was looking and feeling a little bit dated and a wee bit plump. It was built by SGC (an English straight pull AR specialist) about 7 years ago. I picked it up second hand at a bargain price.
The rifle had been specced to represent an SPR type rifle. Everything on it was big… and heavy.
The main drawback to the rifle was the weight. It was well over 10lb with bipod and Leupold Mk4 optic. 10lb+ might be fine for static prone but it gets really tiring when your moving and shooting in multiple positions. I have picked up several shoulder injuries over the years which exasperate the weight issue.


Great in the prone position, not so great to shoot kneeling or standing for long periods.

In the last few years we have seen a transition to lighter components. Supersize ARs are becoming superskinny.. The GnZ AR is going on an extreme diet. The mission – lose a couple of pounds and smooth out those lumps and bumps..

Handguards have become thinner, lighter and more ergonomic. I need to free up some room in the gun canbinet as well so any mod which reduces overall width seems like a good place to start.
The previous handguard is your classic M4 Rail type. It is a great handguard in terms of durability but it is pretty big, very heavy, not the most comfortable for shooting off hand. And so much rail.. I just don’t need that much Picatinny real estate..

I decided to look at a few handguard options. I wanted something that would accept keymod rails or similar. Keymod handguards (and others with similar concept) will accept picatinny sections to the sides and bottom of the handguard. They usually have a built in rail section running along the top but the rest are up to you. The picatinny sections can be added where needed which keeps the weight down to a minimum. It also saves the producers machining 3 of the rails out which reduces the price.

Rainier Arms Evolution 15 Handguard.


The evolution handguards are a Samson/Rainier design which aims to reduce weight, increase comfort and provide accesory options. Both Samson and Rainier have slightly different versions – the difference being the shape of the cutouts. Rainiers version is half an ounce lighter because it has more material cut out. The weight is a svelte 12oz. They are made from 6061 T6 Aluminum which is popular for such applications due to its rigidity.

The Handguard looks great and will definitely give a thinner/smoother overall profile. It is also very hand friendly – No protruding sharp edges, no need for plastic rail covers. Close up inspection reveals no imperfections and overall it looks and feels high quality.


At 15″ long it gives a better placement for bipod. The previous 10″ handguard meant the bipod sat a little further up the barrel than I would like. Placing the bipod further away from you gives a greater level of control and precision due to basic physics. The bipod is a pivot point. The closer to you it gets the more your movements are amplified at the muzzle end. If you need to cover wide arcs of fire quickly that could be a bonus. If most of your shooting is precision based it will be a negative.
The only other mount I am going to install will be for a QR sling loop.


I called in to see Graham and Steve at ACP shooting with rifle and handguard. Graham has kindly offered to help on any modification articles. Although many of the changes you can make to a rifle can be done at home I find having a professional on hand is a great benefit. There is always something that ends up being really tricky which is exactly why I take things to Graham! It also ensures that the articles are giving safe info which is vital from a safety perspective. If your not confident and experienced take the gun to someone who is. Do not attempt modification to a rifle unless you 100% know what you are doing. Again I stress this is why I take it to someone who does.


The first thing Graham does is seperate the upper from the lower. Then it is a simple case of removing the side charging handle, rear T handle and the bolt carrier group. These are all placed to one side. Graham removes the A2 flashhider. Luckily it came away easily as it was recently removed for cleaning. Muzzle devices can easily get stuck pretty solidly due to deposits and grime. If that happens make sure the barrel is held firmly in a soft jawed vice and use a long handled adjustable spanner to create a bit of leverage. Solvents and lubricants can also help as can a little careful heating if someone used loctite to keep it on there..


Graham then places the upper in a specially made vice block which encapsulates the upper beteween two halves. The SGC rifle unfortunately uses a proprietary shaped upper which does not fit a standard block. It was back to the rubber faced vice to clamp the barrel while Graham struggles to release the nut holding the old handguard in place.


After much reddening of the face he is able to remove the quad rail and clean up the threads which have plenty of grime in them. Graham noted that the barrel nut was propietary to the old handguard. The Rainier Evolution requires a standard barrel nut.. Luckily Graham had a DPMS barrel nut in store. Not all good news though as the old one would need to come off.. Indeed it was held on pretty firmly and Graham repeated the procedure of cleaning down all the threads while getting his breath back.


Fitting the Rainier Evolution.


The Thermal bushing.

Fitting the Evolution was a much less difficult affair. The DPMS nut screwed on easily and tightened with an armourers wrench. The Evolution comes with a “Thermal Bushing” in two halves. The two halves must be placed over the barrel nut and then the handguard slides over the top locking everything into place.


There is a slight risk that you may have to fiddle a couple of times to get the handguard properly aligned. There are knurls which need to be “timed” in or
order for the handguard to sit flush.

At this stage Graham encounters another small issue relating to the proprietary upper. The handguard has two “anti rotation pins”. These are basically metal tabs extending from the rear and prevent rotation under stress. The Upper was a little fatter than a standard AR in the area the tabs need to sit, just enough to make the handguard sit a couple of millimeters out from the upper. Graham shaved a tiny bit of material from the underside of the tabs and the fit was perfect.


The anti rotation tab can be seen at the top of the join. The two screws at the bottom are used to tighten everything down.

Once everything lines up Graham tightens two screws at the bottom of the handguard which lock it down tight. For extra safety he uses some loctite blue on them. Remember the handguard experiences terrific force as you fire the rifle. Screws may loosen and let you down under repeated use. Blue loctite makes that very unlikely as it requires a fair bit of torque to break it away.


With much sweating done the handguard install is complete. The rifle is now a good couple of inches slimmer. The Rainier Evolution feels great and has certainly reduced overall weight (saved around 1lb). The next test will be at the range. The AR will be going up to the Welsh valleys for some practical target and then to Bisley for load testing. Both trips will also feature a Rainier Muzzle device to replace the A2 flash


The next article in the series details testing with the new handguard and Rainier muzzle devices.

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