View Full Version : AR-15 Superlight Build

December 15, 2010, 10:30 AM
I'm looking to put together a superlight AR-15 for next year when I finally pick up some property out in the sticks. I'd like to have something to carry around when I'm out there with the dog- had a bad experience with unsavory types (http://thefiringline.com/forums/showthread.php?t=406548).

I've already got a RRA lower that I'll be using, but I'm looking for an assembled upper with a 16" pencil barrel. Ideally, I want a flat-top upper with a low-profile gas block. I'm planning on using some type of optics. I know that Bushmaster makes their ultralight series, but it looks like they only sell the complete rifle. Does anybody make something like this? I would probably replace the front handguard with a plain carbon fiber tube like this: http://www.hiperform.com/hand-guards.htm.

I'm also trying to decide on stock type. The RRA currently wears a MAGPUL MOE collapsible stock, but I'm considering a switch to the A2 if it's lighter. Any thoughts?

Thoughts on optics? I've currently got an Eotech 512, which is nice, but a bit heavy. I'd really like something small, with a 1.5-2x magnification, and MAYBE an illuminated reticle. The Trijicon ACOG stuff is scary expensive, and I'm not really sure where else to look.


December 15, 2010, 10:57 AM
A few different things here.

Upper: If you *really* want superlight, I'd consider a 14.5" barrel with a permanently attached flash suppressor. Bravo Company does sell them, but seems to be out of stock. If you do want a 16" one, then pkfirearms.com is showing several different Rock River lightweight complete uppers for a good price. You'll need to swap out the front sight block for the low profile gas block yourself, but that's not a horrendously difficult task.

Stock: Not sure what the absolute lightest one is, but the MOE isn't all that heavy. Anything lighter would likely be along the lines of the LMT SOPMOD, but bring money.

For optics, you aren't likely to find a lightweight optic that's good for CQB that has any magnification. The EOTech XPS are good, as are the Aimpoint Micros (the H-1 is probably the one I'd recommend unless you want night vision). LaRue Tactical makes a nifty superlight mount for the Aimpoints, so you could get that combo from them. If you want magnification, you could always look to add a magnifier later if you so desire, but the price of Aimpoint + magnifier is within striking distance of some ACOGS. There are the Trijicon Accupoints, but you're still looking at a decent price tag on those. I'd recommend deciding if you really want the magnification or light weight.

December 15, 2010, 11:04 AM
How about 5.7lbs ?


One of the Bushmaster Carbon 15's.


December 15, 2010, 11:11 AM
PetahW- Like I said, I already have a lower and don't really want to buy a complete rifle. I am intrigued by the carbon series though, maybe when I have a bit more cash on hand :D.

Techno- I'd like to keep it to a 16" minimum for versatility- ideally I'd like good performance from 10-150 yards, maybe a bit further. I actually found on Pkfirearms that Bushmaster offers the complete uppers to their superlight flattop series, with the pencil barrel profile. It's about 2/3 down the page here: http://www.pkfirearms.com/Bushmaster_Barreled_Uppers/56/c.

December 15, 2010, 11:35 AM
I am intrigued by the carbon series though, maybe when I have a bit more cash on hand

Complete junk.

December 15, 2010, 12:27 PM
Complete junk.
Please elaborate why.

December 15, 2010, 02:26 PM
Thinking about this for the sight: http://www.trijicon.com/user/parts/products1.cfm?PartID=850&back_row=0&categoryID=13. 1.2 Oz without the mount, that is TINY. I'd prefer something with a little magnification, but small+light+magnified looks hard to find.

December 15, 2010, 02:34 PM
You might want to look at the Daniel Defense LW uppers here. I recommend a16" LW midlength as it's an excellent compromise and the price is incredible for something of that quality. In fact I just ordered one last week! Of course if you want to cut more weight a 14.5" LW with carbine gas system would be a few oz. lighter.


December 15, 2010, 03:56 PM
As far as reducing weight on the front end, I'm wondering if I can just use an upper with a standard front sight and cut off everything above where the gas tube comes in (and finish it so it looks pretty). That seems as though it would be lighter than some of of the aftermarket gas blocks, which at best are like full length wrap-around tubes. Plus, I don't like ramming set-screws into my barrel.

December 15, 2010, 04:13 PM
As far as reducing weight on the front end, I'm wondering if I can just use an upper with a standard front sight and cut off everything above where the gas tube comes in (and finish it so it looks pretty).

You can. I've done it before, but I'm not good enough with detail work for it to look all that great. It can look decent through. AR15.com has had threads on this, but a quick look didn't show where I had seen them. Basically, you take a hacksaw and Dremel to the thing. Chop off what you don't want, sand it down, and then black high temperature paint (like for a BBQ grill) isn't too far off the original anodizing.

The plus side is that you can get it down to an extremely low profile while also retaining the ability to use the original taper pins. The downside is that there's no going back- if you decide you ever want the original type FSB back, it's either set screws or a real pain in the rear- the taper pin holes in the FSB and barrel are usually drilled together; consider them a matched set. You can't just get another FSB and throw it on.

Edit to add: found the thread with the info. It's HERE (http://www.ar15.com/forums/topic.html?b=3&f=4&t=226782), in a post between 1/2 and 2/3 the way down the page.

December 17, 2010, 11:59 PM
DPMS upper from Midway has everything you need for under 400.00$

The quality is there also.


DPMS AR-15 Flattop Upper Assembly 5.56x45mm NATO 1 in 9" Twist 16" Bull Barrel Chrome Moly Matte with GlacierGuard Handguard

December 18, 2010, 01:15 PM
I have a BCM standard 14.5" upper w/ permanently attached FSC556 mated to a Cav Arms lower. When I had a DD 1.5 rear sight mounted and loaded 20 round USGI mag...it weighed in at 5lbs 15oz. I have since upgraded to a Nitrex 1.5-5x32 scope and burris pepr mount and magpul MBUS rear sight it is still under 7.5lbs.

The cav arms lower is ~1lb less than and traditional A2 stock and aluminum lower and ~4oz less than a USGI 4 position stock and aluminum lower.

December 18, 2010, 09:47 PM
I put together a Cav-Arms lower with a standard DPMS parts kit.
I put a Bushmaster 7.62x39 upper on it; 16" barrel. I use the carry handle for my sights b/c they're not bad. It cost a little above 600.
It weighs 6.4 empty. I would think you could hit 6 lbs without trying hard or breaking the bank.
Good luck with that!

December 18, 2010, 10:09 PM
My idea of a lightweight AR is my M16A1 clone built with a surplus GI upper...7.4lbs with sling and loaded 20rd mag. Full 20" barrel, and I can hit a clay pigeon at 100yds with the A1 iron sights.

December 19, 2010, 01:28 PM
Bushmaster sells just the barrels. I bought a complete barrel assembly last year for like $230. 1-9 chrome lined.

December 19, 2010, 02:48 PM
Gamehog- I really don't want a bull barrel on this thing. I'm really only considering pencil barrel profiles. Even the govt profiles I've got on my uppers right now are heavier at the front than I'd like.

Actually, does anybody make a barrel profile even lighter than the pencil profile? I realize this wouldn't be standard, I'm just wondering if anybody makes one. I feel like you could keep the standard pencil thickness around the chamber and first few inches of the barrel, and then taper it down somewhat toward the muzzle (where pressures are lower).

December 19, 2010, 11:01 PM
The pencil barrel is about the lightest. It gives you more bang for the buck in lightness than any other modification. After that, a small lo pro gas block will be lighter than a cut down FSB. With a tube over it, it will be protected. Set screws don't really need to be jammed into the barrel, just drill a dimple and use Loctite to keep them in. That's less damaging than the GI taper pins getting drilled across the bottom of the barrel installing the FSB.

Adjustable stocks sound lighter because of the shorter carbine tube, but with heavy buffers, extra hardware to lock them up, etc, an A1 rifle stock can do the job just as well, plus add rifle reliability. The original M16 with pencil barrel can weight less than a tricked out M4gery, especially one with a quad rail.

December 20, 2010, 12:00 AM
With a Cav Arms polymer lower and a CMMG 14.5" pencil barrel with a pinned and welded Phantom this comes in at 5.0 pounds:

While it accomplished the objective of building a very light AR, I was never thrilled with the CMMG barrel and that Cav lower's triggerwell has nonstandard dimensions that precluded using my preferred LMT or Geissele triggers. And, light though they are, the Magpul MBUS set is not satisfying as a primary sight.

So it's being rebuilt to sacrifice some weight savings for enhanced functionality. The new barrel will be a 14.5" Daniel Defense pencil barrel with a permanent muzzle device (Phantom or Battlecomp) and a Micro gas block.

The only parts going forward besides the charging handle will be the slickside upper receiver (no forward assist or brass deflector saves ~4 oz.):

And the skeletonized Young N/M chrome bolt carrier (also saves a few ounces):

An Aimpoint T-1 will be used solo, and since there will be no irons with which to cowitness Aimpoint's low riser (1 1/8 oz. less than a LaRue LT-660) will be used:

The PRI free float forearm will be replaced by a Troy TRX for another 2-3 oz. savings.

Going to a standard lower will allow me to use a Geissele SD-E trigger, and the stock will be a Fiberlite CAR, which I prefer over the A1, and it will use the lightest (and my favorite anyway) grip, an A1. And a tad more weight will come with a troy mount for a Surefire G2-LED light. The Ace UltraLight is another very light stock, but I find it's A2 length just a tad too long.

Hope that helps.

December 20, 2010, 09:18 PM
I built this one to be as light as practical:


December 20, 2010, 10:26 PM
bushmaster redid the carbon 15, i dont know anything about it but it is suppose to be improved over the old design



December 20, 2010, 11:23 PM
No foward assist? Smaller ejection port? These are improvements?

December 20, 2010, 11:41 PM
RRA Elite A4 Middy with a CTR and an Adco pencil 14.7" bbl w/A2 FH perm installed.


maestro pistolero
December 20, 2010, 11:57 PM
It's the next one listed on the same Midway page as the Bull barrel. Pencil barreled, complete upper for $399. I have had noting but good luck with DPMS, and I've had WAY more expensive ARs.


December 21, 2010, 12:29 AM
Actually, does anybody make a barrel profile even lighter than the pencil profile?

Found this shop that dimples barrels. If or how much lighter it would be I don't know.