My Mid-Length AR Build

[Vic]

Some Background (A little about me and a little about the kind of rifle I’m building):

For about a year now I’ve been thinking about building an AR but the political climate has made parts either expensive or hard to get until this summer. I’m not LE/AF nor am I a 3-gun shooter or really all that much of a “gun guy” (whatever that means) though I do enjoy shooting. I did serve in the military, but in a noncombat rate so any formal training was limited to shooting a shotgun and a 9mm pistol back in 2002. My primer for the AR platform has been Kyle Lamb’s Green Eyes & Black Rifles, which an infantry buddy of mine suggested I read. I’ve been to the shooting range semi-regularly with friends and coworkers since then, but that has tapered off in the last few years since I started school.

This will be my first AR and so I’ve decided that I would start with something fairly middle of the road, an AR with a 16” barrel and a mid-length DI gas system. I decided on the 16” barrel as it would allow me to swap out compensators, flash hiders, muzzle brakes, etc. without worrying about breaking the law (as I can’t own a SBR in Washington State) or spending money pinning and unpinning. A mid-length gas system seems to make sense from what I’ve both read here and heard elsewhere. This AR will be my primary AR on which I will not only learn more about the system, but also how to “drive” it.

As this is my first AR, I decided to build it from scratch for several reasons. I acknowledge that there are many good reasons to go with a manufactured AR from Colt, BCM, and Daniel Defense, or at least a prebuild upper. However, I decided against that approach because of three main reasons: cost, availability, and the desire to build it myself in order to both understand how the parts go together but also because I enjoy building things. Additionally, this would allow me to conduct research into what parts to get and avoid the “shoulda/woulda/coulda” syndrome as best as I could by purchasing parts at what I consider a point prior to that of diminishing returns but at the same time not cheapening out. I believe that there’s a sweet spot when it comes to pricing.

My Lower Receiver Parts Selections (What I’ve bought, what I’m considering, and why):

• Stripped Lower Receiver : MEGA Arms Forged Lower Receiver (I decided on this one because it is a well-build forged lower that should have very little problems in terms of compatibility with other parts. Also, I happen to like the Mega Arms logo and they are a local company.)
• Lower Parts Kit : Rainier Arms Lower Parts Kit w/o Trigger (I don’t know much about triggers so I thought I would get a lower parts kit sans trigger and put the money towards a better trigger such as the ALG QMS or ACT based on the reviews both here and elsewhere.)
• Trigger : ALG QMS (Visited Rainier Arms and tried both the QMS and ACT and decided to go with the QMS. Thanks UWone77.)
• Receiver Extension : Damage Industries Complete Buttstock Kit (It’s Mil-spec and made of 7075 aluminum. Also, it was on sale and money saved here can be better spent elsewhere.)
• End Plate / Sling Plate : IWC QD End Plate (A buddy has one of their light mounts and it was well built. The fit and finish on the IWC plate looked really good in the photos and I like the fact that it’s steel so I can stake the castle nut properly though I’m sure an aluminum plate could be stakes just as well.)
• Stock : Magpul CTR, Mil-spec, Black (I bought this because shooting a carbine with this stock on it was comfortable for me and it locked up solid.)
• Pistol Grip : BCM Gunfighter Mod 1 (I was able to handle a rifle with this mounted on it and found it comfortable to hold with my elbow tucked in. So I bought it. Stickman’s review on GearScout also helped so thanks!)

My Upper Receiver Parts Selections (What I’ve bought, what I’m considering, and why):

• Stripped Upper Receiver : MEGA Arms Forged Upper Receiver (I bought it with the lower for the same reasons.)
• Forward Assist & Dust Cover : Damage Industries (I was purchasing the lower receiver extension from them and these parts were priced competitively with other parts elsewhere.)
• Charging Handle : BCM Gunfighter Mod 4 Charging Handle (Again, it was on a friend’s rifle and I liked it. It was also on sale and marked down to $10 more than a standard charging handle.)
• Bolt Carrier Group : Rainier Arms, Phosphate (I don’t think I need a NiB bolt for my first AR. Rainier Arms is local and they stand behind their products. It was also on sale, which made up for the fact I didn’t bring cash with me to the grand opening.)
• 16” Barrel : Centurion Arms 16" Hammer Forged Light Weight Barrel (I bought this because I’ve read that the BCG and the barrel are the heart of the AR so I felt that if I was going to spend extra money on something, this would be it. I had been considering several different barrels including those by Black Hole Weaponry, Rainier Arms (out of stock), BCM (both their standard and CHF barrels), and Daniel Defense. A friend of mine suggested that I look at Centurion Arms due to their accuracy and their construction, I couldn’t go wrong. Also, the company is owned by an active duty member so that’s always a plus.)
• Low Profile Gas Block : Geissele SGB (I bought this because I went with a Geissele SMR. The other options, such as the Rainier Arms, Centurion Arms, and Fortis Pinnable gas blocks I had been considering earlier would all have worked just as well though.)
• Mid-length Gas Tube : I’ll probably go with a gas tube from Rainier Arms. I don't understand all the different coatings or see their need.
• 12-15” Free-Float Rail : Geissele SMR Mk1 15" (See the follow up post for my rational. I did manage to find one at 10% off which helped with the price difference.)
• Muzzle Attachment : I’m not sure what I want though I’ve narrowed it down to several models including the AAC Blackout (non mount), Fortis RED, Rainier Arms XTC and XD. I’m open to suggestions on this as I want something that I can use at a class in the future.)

Sights/Optics/Accessories (What I’ve bought, what I’m considering, and why):

• Iron Sights : MAGPUL MBUS Pro (On loan from a friend)
• Optics : Probably an Aimpoint Pro or maybe an EoTech XPS? I’m not sure yet.

As you could probably tell, I’ve purchased a majority of the items in my list and am waiting for them to show up. I did quite a bit of research on this site, especially through the “Extreme Use AR-15” and the “Explain your AR15 layout” topics, which I hope is reflected in my parts selection. That being said, any and all suggestions and advice is highly appreciated as I’d rather learn from another’s experiences than my own mistakes (it’s cheaper and less painful). As parts arrive, I’ll post pictures of them and hope to answer any questions others may have as well as keep my build progress up to date. Here’s a picture of the upper and lower receiver (reposted from the Mega picture thread) to get things started:



*Items in gray have been purchased.

[UWone77]

Great start!

I'd go with the QMS over the ACT. Biggest factor is cost, and they are the same trigger, the ACT just has the Nickel plating.

Solid selection for the Barrel, and other main components. Looking forward to seeing your build progress.

[LMMzach]

Great write up looking forward to see progress on this!

[Vic]

I stopped in Rainier Arms today and picked up my BCG and the ALG QMS trigger after spending time talking to several folks there and trying the two different triggers (QMS & ACT). I also spend some time with the various rail systems trying to determine what length would work best for me and I think I will be going with a ~14-15" rail system. When I got home, there were some parts waiting for me so I figured I'd post up pictures of the parts.

Mail Order Parts:



Close Up of the parts from Rainier Arms LPK w/o Trigger:



I don't know who the OEM is for the lower parts kit, but all of the parts look well made.

Rainier Arms Walk-In Parts:



Now that all of the parts I need for the lower receiver arrived, I'm now waiting for barrel to arrive and am going to look into which rail system to go with.

A big thanks to everybody at Rainier Arms for their help and to everybody for their suggestions and feedback,
Vic

[Vic]

Since all of the lower receiver parts had arrived, I decided to spend some time today assembling them and installing the dust cover and forward assist into the upper receiver. This was so I could mock everything up and see if there were any issues. The charging handle is installed for the photo, but there's no bolt carrier group installed as I need to bring both it and the barrel down to Rainier Arms to check headspace. Assembling everything took me about an hour as I wanted to make sure I did everything right the first time. The spring pin for the trigger guard was the hardest thing to install as it was an extremely tight fit and I had to polish and lubricate the pin first, hence the discoloration there. Additionally, I will have to torque and stake the castle nut as it's just on there finger-tight for the time being.





While not pictured, the Centurion Arms barrel arrived today. It was packaged in a Premium Metal Guard bag with a plastic thread protector around the barrel threads. There's a Centurion Arms bullet rollmark near the muzzle and the number "86" near the barrel extension. Overall finish looks pretty good and I'll post a picture of it later on once I decide on a rail.

Thanks for following along,
Vic

[mustangfreek]

Nice build, i have a mega build im slowly working on also. I like your ideas on rails, but have no insight as i have similiar choices and cant make up my mind either.

[UWone77]

Nice to see the SGN crowd on this side!

[Army Chief]

Good thread, quality parts and a competent approach to the build. It seems that the trend has turned toward stripped-down lightweights so much of late that I was almost surprised to see a fairly-conventional mid-length project (notwithstanding the LW barrel); that said, these rifles remain a consistent favorite for good reason.

I suspect this one will serve you well.

AC

[Vic]

Thanks for all the feedback. Things are progressing smoothly and I finally settled on a Geissele Mk1 SMR rail. I made this decision by taking into consideration several different factors: ergonomics, features, price, & weight. Several of these factors, ergonomics and intended use, are subjective while others, price and weight, are objective. I've included a short breakdown to give some insight into my thought process:

Centurion Arms CMR 14 -

• Ergonomics: Slim (1.56") low profile tube that's pretty comfortable to hold. The sides are pretty solid with the vent holes at top and bottom right and left.
• Features: Four built in QD swivel mounts & barrel nut that doesn't require timing but does require a spanner. Rail has build in anti-rotation lugs which is a plus.
• Price:$315 MSRP w/o any rail panels or barrel nut wrench. It's a machined rail with great fit and finish, which is reflected in the price.
• Weight: 11.6oz with barrel nut and hardware.
• Thoughts: I really liked this rail and it was my second choice. It was the best mix of build quality, weight, features, and it is the same company as my barrel. However, I've read that they can have compatibility issues with certain low profile gas tubes. If it was a 15" rail, I might had gone with it.

Geissele SMR 15 Mk1 -

• Ergonomics: Slim (1.7565") low profile cross that's also pretty comfortable.
• Features: Two built-in QD swivel mounts, 3 rail panels, barrel nut, & proprietary wrench. Rail has built in anti-rotation lugs, which is a plus.
• Price: $375 MSRP w/ rail panels, barrel nut, & wrench. It's another machined rail with great fit and finish, which is reflected in the price. Whether the $60 difference between CMR and SMR offset the additional parts is up to you to decide.
• Weight: ~20oz with steel barrel nut and hardware but not the rails.
• Thoughts: I decided on this rail more because of the features and ergonomics than because of weight and price. I also found one for 10% off which made the price far more reasonable. Because of the reduced price difference between this and the CMR along with the added features, it made more sense for me as I wanted a rifle that while not an "extreme" AR, was a solid range rifle and tool.

Noveske NSR 15 -

• Ergonomics: Slim (1.48") low-profile tube with a slightly more square cross section. Sides are covered with key mod slots.
• Features: Comes with a barrel nut, mounting hardware, and T25 wrench. The anti-rotation pin in the upper part of the rail required either a Noveske upper or a hole drilled into your upper. You need to time the barrel nut to align the holes in it with the mounting holes in the rail.
• Price: $289.95 MSRP w/o rail panels or barrel nut wrench (1 1/16" crow's foot wrench).
• Weight: 11.6oz
• Thoughts: While substantially cheaper and lighter than either the CMR or NSR, it's design goal of "being the lightest and smallest free floating forend option to the M16 family of weapons" really didn't appeal to me. Additionally, the need to purchase additional panels and a wrench also discouraged me.

Rainier Arms Evo 15 -

• Ergonomics: Slightly wider than the other options at 1.8" and the rail has a more facetted design. The sides are pretty solid with the vent holes at top and bottom right and left, much like the CMR but these are triangles.
• Features: Comes with QD swivel socket, 2" rail panel, and 4" rail panel, and heat sinks. It uses the stock barrel nut which is a plus if you are adding this to an existing build and/or have a stock barrel wrench already. Additionally, it has two anti-rotation lugs.
• Price: $199.00 MSRP w/ rail panels and heat sinks.
• Weight: 12.80oz
• Thoughts: In terms of bang for your buck, the Rainier Arms Evo rail is pretty good. However finding it in stock is difficult. Because of this lack of availability, I didn't go with it. Additionally, because I was building an AR instead of working from a pre-existing AR.

Since weight was brought up in a reply, I've decided to compile the weight of the build (Measured w/ Digital Postal Scale) -

Complete Lower (w/ Carbine Buffer) : 2lb 3.5oz
Upper Parts (Bbl, BCG, Charging Handle, & Upper Receiver) : 3lb 0.6oz
Total So Far : 5lb 4.1oz
SMR Mk1: ~20oz
Gas Block & Tube: ~2.5oz
Muzzle Device: ~2.5oz
MBUS Gen 2: 2.5oz
Proposed Total: ~7lbs w/o magazine or optics

Here's a picture, abet a bit fuzzy at the barrel extension, of the Centurion Arms barrel. It's very similar as far as I can tell to a M4 profile barrel with most of its "lightweight" profile being after the gas block.



Barrel Profile Diameters* -

A - Near the Barrel Extension : ~.97"
B - Forward of Reduction : ~.66"
C - Before the Gas Block Seat Flare : ~.60"
D - Gas Block Seat : ~.75"
E - Between Gas Block Seat and Muzzle Threads : ~.68"

*These were taken with a plastic General-brand caliper so these are only to the hundredth's place as their accuracy is not absolute. I'm providing these figures for others looking at the barrel as some of the images I found online were not very helpful.

Now to figure out the gas block and muzzle device situation,
Vic

[Vic]

The Geissele rail arrived yesterday and I took some pictures of the gun mocked up with the rail to figure out how the balance would be. With the CTR stock extended, the balance point is T12. With the CTR stock collapsed, the balance point is T13. The bolt was installed for this test. Right now I am awaiting the gas block and gas tube. With the addition of the gas block and flash hider, I expect the balance point to move forward, but not substantially. The Mk1 comes with a steel barrel nut, which adds roughly 2 oz, but I didn't see the need to purchase the lighter aluminum barrel nut.



Any feedback, both on the rifle and my lackluster photography skills, would be appreciated,
Vic

[GOST]

Looking very nice. What muzzle device are you deciding between?

[Computalotapus]

Looks very nice. Can't wait to see it dressed out

[Vic]

Thanks guys,

I was considering the AAC Blackout (non mount), Fortis RED, Rainier Arms XTC and XD, but several things have complicated my decision. First, Rainier Arms is releasing a new XTC. Second, a friend of mine has sent me a PWS FSC 556.

No point looking a gift horse in the mouth,
Vic

[LMMzach]

Coming along man!

[JimmyT]

Good looking rifle! Let us know how it shoots!!