View Full Version : Advice on a AR (M16A4) build

09-07-2008, 8:15 PM
Hi everyone,

This is my first post on calguns; and I'm looking for some advice and clarification that I haven't been able to find searching the forum on an AR build I've wanted to do for a while.

My goal is to get an OLL AR that is as close to an M16A4 as possible. Obviously the lack of burst fire and the need for a maglock are where it differs, but oh well.

From wikipedia (http://en.wikipedia.org/wiki/M16A4#M16A4) I've been able to figure out the following are the distinguising factors over the A2; flat top with a picatinny rail instead of a carry handle and a Knights Armament M5 RAD instead of the 'normal' A2 barrel shroud.

Now I need some advice sourcing the parts and i've been looking mostly at Stag as the mfg.
So far I've found the lower half; http://www.stagarms.com/product_info.php?cPath=18_32&products_id=238
I'm fairly certain that one is correct, just wanted to make sure.

I've also found the Knight's armament M5 RAD; http://www.knightarmco.com/shop2/index.php?productID=143

This leaves me needing an Upper and a 20" barrel to accomodate the M5 RAD. (I Think)

This is the list of Stag Uppers; http://www.knightarmco.com/shop2/index.php?productID=143
(This is where I need the most help).
Stag has all of their uppers listed as "A3" flat tops, but if Wikipedia is to be believed their designation is incorrect, as the A3 upper would be the same as an A2. And that would mean that what Stag has listed as their A3s are in fact A4s.
If that IS the case, and Stag's designation is simply wrong, then I'll get one of their complete right hand uppers. But if that isn't the case, and the Stag A3 upper is in fact different from an A4 upper, where can I find a true A4 style upper?

Second thing I need help with is the barrel. Stag only has one set listed for sale as a standalone item, a 16" barrel assembly (http://www.stagarms.com/product_info.php?cPath=15_36&products_id=294), which I'm guessing is unuseable with the M5 RAD, since on the Knights Tactical website it says it is meant for a 20" barrel.
I know on the Stag model 4h the rifle has a 20" barrel (probably the kind I am looking for) but can anyone verify and then tell me where I can buy just that barrel assembly? If they don't sell it separately, is there another mfg. that has one of those style barrels? I don't want one of those heavy bull barrels, atleast not on this build, but those are the only other 20"s I can find.

I think that is all I need for the build:
The lower half

The upper assembly (if it a correct A4 upper)

The barrel assembly

The M5 RAD

And of course a bullet button.

Any advice or verifications would be helpful so I know I've atleast got the right information. And of course if you could link to a standard 20" barrel assembly that would be awesome.

Thanks all - Ed

09-07-2008, 8:26 PM
For the upper you might be able to save yourself some time and trouble by getting a RRA Standard Length Upper with a 20 inch 1:9 Chrome Lined barrel and then swap out the handguards for the KA M5 RAD.


09-07-2008, 8:33 PM
Welcome to Calguns!

A4 is a rifle designation. The A3 is often used as a "flat-top" designation.

You can get Colt rifle uppers, if you want to pay for them.

The RAS you have there is VERY over priced. I picked one up recently for about 1/3 of that.

Skip building the upper yourself and buy it complete. Just buy something like this below and replace the plastic handguards:
It includes a detachable carry handle on the flat-top. If you don't want that, consider this...

CMMG will be more to mil-spec, with the 1/7 barrel.

Can I make a bold statement and suggest you step out of the "A4 clone" box and put a free-float rail in place of the RAS? It will give you much better performance at a similar price point. You'll get the same look. The LaRue or Daniel Defense M4 rail will give you a more traditional look.

If you want a USMC M4 clone you'll want an ACOG RCO-A4 and a Matech or KAC 600m back-up iron sight. The mag pouch on the A2 stock is a nice touch, too.

Lastly, to make sure you're kosher with legality, read through this:

Mssr. Eleganté
09-07-2008, 8:49 PM
I built an M16A4 look-a-like using a Stag 4H upper and a KAC M5 RAS

Just keep an eye on the classified section at AR15.com for a KAC M5 RAS. I bought my first M5 RAS for $300 on sale from an online vendor, plus another $65 for the forward vertical grip. Then some guy was selling brand new ones on AR15.com for $200 shipped with the vertical grip included, so I got another one.

The KAC M5 isn't very well regarded these days and is considered outdated. So guys tend to sell them for very cheap on the trader boards. Do not pay $350 for one!

The ACOG scope ended up doubling the cost of my A4.

09-07-2008, 9:31 PM
Cool, those options would save me a bit of time and money, and thanks for the heads up on the KAC M5

I suppose I would go one of two ways; the RRA customize it yourself thing gives me basically a stock upper that is a bit cheaper than the Stag 4H - but is there any noticeable difference in quality between the two?

@ ucla - thanks for the suggestion about the free-float rail. Got a question though; http://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_id=267
In the options box for selecting a handguard it lists a Daniel Defense Quad 12.0 for $350.00.
Is that the M4 style one you were referring to?

The CMMG 20" uppers look good too, http://cmmginc.secure-mall.com/shop/index_auto.php?shop=1&cart=1240810&cat=27&

Would it be wise to pay what either of them are asking for a DD free float quad rail or should I try to find one wholesale?


09-07-2008, 11:29 PM
heres one.. should be a milspec bolt carrier and 1/7 twist.

09-08-2008, 10:40 AM
That used one would be a good way to go, pending round count.

I'd put CMMG>RRA>Stag. That price for the DD is a bit high, but it won't come down much, especially compared to a KAC RAS, which drop a ton. The advantage of the DD is it's actually free-floating (not touching the barrel) which enhances accuracy - especially since you're planning optics.

I don't know whether RRA installs M4 or Lite rails. You should look at them on DD's website and determine which you'd prefer. They weigh about the same, but the Lite rail has a steel barrel nut and looks more integrated. The M4 will give a more traditional look. LaRue is similar in appearance to the M4.

Before ordering from RRA or CMMG, contact the site sponsors. I'm confident they'll be able to help you and maybe (probably) get it to you sooner for less money.

09-08-2008, 2:41 PM
Alright I think I'm comfortable with where I'm headed with this.

For the upper half I'm leaning towards a CMMG 20" MedCon assembly with a DD 12.0 Lite rail.

About the lower, would it be advisable to pop the extra $100 or so and get a CMMG lower half, or would one of the Stag lower halves work just fine?

Last question I have is about the huge list of internal options that CMMG has listed.
The LMT or EGRESS bolt carrier upgrades I can rap my head around and they make a bit of sense, but what is the point of getting one of the 10 or so redesigned gas blocks they have listed?
Same question about the CMMG lowers; what is the point of upgrading the endplate adapter, buffer, or the hammer and trigger pins? Would those options just be for show, or do they actually add something structurally to an AR that I should want?

Thanks for the advice so far guys, it has been realyl helpful.

09-08-2008, 4:49 PM
On a 20 inch upper with a 12.0 rail you dont need to change gas blocks.
Your front site gas block is fine.

The KNS trigger pins are IMO worth the money. Keeps the pins in tight and just takes another thing off the list to think about.

No real recoil in a 5.56. Save your money and pass on any upgraded buffers.

Post pics when your done.

09-08-2008, 5:07 PM
LMT and EGRESS upgrades are for carbines. Not necessary for rifles.

Stag lowers are great. No need to change. If you want to match in the future, it's fiine.

The M16A4 uses a standard FSB, so no need to upgrade. The other gas blocks are for low profile (no sights or under the rail) and/or folding sights.

Upgraded endplates are for various sling mounting options. Different buffers are for different gas systems (H-buffer is for overgassed carbines, etc). Thousands of guns run without KNS - no real need (especially on a semi-auto). They're the choice of mall ninjas everywhere ;) They do look nice. They're really great for guys with registered FA lowers to keep from making their hammer holes oblong.

09-08-2008, 6:25 PM
Well I think that about answers all my questions, and I think I've got the basic setup all figured out (minus the accessories).

Upper - CMMG MedCon 20" A3 flattop, badger gen-II tac latch, extended feed ramp, normal A2 post, normal handguards (I'll get a DD Lite rail from their site later) and a Phantom 5C1 flash hider.

Lower - I realized that the CMMG is only about $10 more for the basic lower half than the Stag - thought it was more because I had already added options, anyway...
CMMG lower with an A2 butt, normal buffer, endplate and trigger. MIAD grip, ambi-selector, KNS hammer and trigger pins, gapper and a pivot pin sling adapter.
And my bullet button.
Anything else I need?

Post pics when your done.

Will do, not gonna start building for a while though, probably a few weeks.

09-08-2008, 8:11 PM
You'll need a rear sight... optics, if desired.

Why bother upgrading the FH? Standard A2 is more "real." KNS aren't really necessary, but it's your $ - I'd spend the cost of those on a 2-stage trigger upgrade. ;)

09-08-2008, 8:19 PM
Well I can tell already I'm going to be building two.

One will be a vanilla M16A4, the other will just be a civi clone with whatever tasteful features I can think of adding.

Too many options on these AR's to have just one.

09-08-2008, 8:40 PM
Well I can tell already I'm going to be building two.

One will be a vanilla M16A4, the other will just be a civi clone with whatever tasteful features I can think of adding.

Too many options on these AR's to have just one.

That's the spirit :) They're like tinker toys anyways - you can switch as you go.

09-08-2008, 9:20 PM
The easiest way to get a "correct" A4 is to buy one from Sabre Defence.
They were recently awarded the newest contract for M16A4 for the Navy and Marine Corps (as of July). So if you buy a Sabre A4, you will be essentially getting the real thing.

Sabre is far higher quality than Stag or RRA, they use 4150 CMV barrel steel (like Colt and LMT) and are 1/7 twist. Both of which are in the M16 TDP.


09-08-2008, 9:34 PM
Excellent link Pryde, thanks.

I'll have to keep sabre in mind.

09-08-2008, 9:34 PM
Excellent link Pryde, thanks.

I'll have to keep sabre in mind.

Here's a dealer that has them in stock.


The stag will probably be cheaper, but if you want the real deal of course it will cost more.