Lightweight AR15 Build: What Matters Most?

Status
Not open for further replies.
Justin

Justin

Moderator Emeritus
Joined
Dec 29, 2002
Messages
19,567
Location
THE CHAIR IS AGAINST THE WALL
So, if I wanted to build a lightweight AR-pattern rifle, what components are the ones that will offer the best weight-savings bang-for-the-buck?

for instance will a lightweight barrel save me more weight than a skeletonized float tube?
 
Barrel is a huge chunk of weight. Short and thin will go a long way on weight reduction. Couple that to a Slickside upper and your saving a bit more. Other parts are pretty well standard. A polymer lower reciever will save a bit but not much.
 
I think the old fashion, short plastic handguards are lighter than the aluminium quad-rail ones.

Go with polymer back up sights.

Colt bolt carrier that has been milled all the way out on the bottom.

Polymer frame and polymer buffer tube for weight savings.

No frills (ambidextrous safety, ambidextrous magazine release, ambidextrous bolt stop release, ambidextrous charging handle, no flash suppressor, no stabby thing mount on the front sight base).

Single point sling mount.

Collapsable stock.
 
Very nicely said Gary....no stabby thing mount...I like it.
And yes, the polymer handguards are lighter than metal...both on the gun and on the pricetag.
 
As they said, the barrel is the biggest weight saver. 16" pencil profile with your choice of gas system length, carbine or mid length.

Put on a low profile gas block and smooth aluminum free float tube (no rails) and flip up sights. I got a tube from Midwest Industries that weighs about nine ounces.

Single point sling, as mentioned by Gary.

Personally, I'd stick with aluminum for the buffer tube and lower. Saving weight forward of the receiver makes a much bigger difference in handling than weight at or behind the receiver. Same with bolt carriers. Lighten things up too much and you might (not will, might) have issues with overgassing due to not enough weight in the carrier.

However, if this is strictly about a number on a scale, ignore my previous paragraph.
 
Actually the polymer handguards weigh more, when the delta ring, spring and front sight tower are included, than an aluminum free float tube like the Midwest Industries SS and BCM KMR used in conjunction with a polymer front sight.
 
Yes, charts are out there with weights on handguards vs free floats. The aluminum tubes can be lighter sans rails with lots of holes in them. How they mount also affects it.

There are sources for titanium parts and folks have built AR's well under 4 pounds.

http://www.ar15.com/forums/t_3_4/359047_.html

The majority of the weight savings is to delete the FSB and relieve barrel weight to the minimum. After that the bolt carrier, then skeletonized the lower and upper.

http://www.bing.com/images/search?q...ecievers&qpvt=skeleton+AR+recievers&FORM=IGRE

The MFT Minimalist is one of the lightest stocks under 6 oz.

It's a fun hobby but under the 5 pound mark costs start going up geometrically. I have a 10.5" AR pistol at 5.5 pounds, the 6.8 16" deer rifle is 6.5 pounds with a recon weight barrel. Nothing at all to brag about - but back in the day of heavily tricked out quad rail M4geries weighing 8-10 pounds they are light. After a full day's still hunting thru dense brush you notice an extra pound easily.

It's the same game mountain rifle builder's get into, how much weight can be lost affordably and still carry enough gun?
 
Barrel is #1, followed by handguard, then stock choice, receiver style and material, bolt carrier, etc.

Pretty easy to build a ~5 lb carbine today with the right barrel, handguard and stock. A Faxon 14.5" pencil barrel with permanent Ti muzzle device, a 10" BCM KMR handguard and one of the lighter carbine stocks like the MFT Minimalist will get you there using standard upper & lower receivers.

I think the old fashion, short plastic handguards are lighter than the aluminium quad-rail ones.
Click to expand...

Once you factor in the barrel nut/delta ring assembly, end cap and FSB, a lot of aluminum FF handguards with low profile gas blocks are lighter than stock plastic furniture.
 
I built an AR recently with two goals in mind: 1) light weight and 2) smooth and minimal recoil. I had prior experience with A1, A2, and M4-type rifles and liked the smoothness of the A1 and A2 and the lightness of the A1 and M4. I went with an 18" rifle-length pencil barrel to get the longer, smoother gas system while still watching weight and went with the Vltor A5 buffer tube system with the MFT Minimalist stock for once again smooth recoil and light weight. I went with the MI SSM handguard for weight, but blew the weight budget a bit with a PRI folding front sight gas block since it was the only option for a folding front sight on a .625 barrel. That was a bummer but I felt that a barrel-mounted folding front sight was important to me. Also, if you are planning to use a scope I like my Aero Precision mount. It is about half the weight of anything else in its price range, and about 2/3s the weight of pretty much any other mount.
 
-Barrel turned so narrow it wanders badly after three shots
-Tiny, vestigial sights instead of a rail (think WWII pistols)
-SBR, preferably <3" with an approximately 1" gas system (it's been done successfully)
-Polymer upper/lower receiver
-Ultra-short buffer tube (I've seen ~5" models out there)
-Tennis ball in lieu of a real stock
-No front handguard, just use the magwell or mittens
-Pistol grip cut down to two-finger derringer specs
-Titanium trigger guard

You're welcome :evil:

TCB
 
Barrel, handguard and stock are all great places to save weight. But a huge area that most people neglect is the optic. Time and again I see people saddle a 2lb optic/mount on a 5.5lb rifle... My Aero Precision mount with a Leupold 2-8 VX3 weighs in at only 14oz combined.
 
Stocks can be amazingly heavy. If you're gonna use a lightweight front end, don't forget to pick a lightweight back end. I prefer the MagPul SL for my lightweight builds.
 
I went to a large gun show yesterday and am left with the question if the only places to choose a lightweight upper is on the Internet.

Lots of upper assemblies to choose from. Most of them had aluminum handguards. Probably free floated with interesting designs cut in them to reduce weigh but I suppose mainly for looks.

The only M-4 type upper I saw was in 300 Blackout. By the way .300 uppers were common.
 
Last edited:
I can't really add much to the excellent posts above - seems like 5.5 or so pounds is a practical limit for me. Barrel (and some stocks) are where the mass is. As with anything engineered there are trade offs. A 5.5# rifle is pretty light!
 
why not just fill a balloon with helium and tie it to your carry handle? makes about as much sense as some of the other things people do to their ARs to make them ridiculously light
 
Remember .... it isn't just about weight ... but balance as well.

The less weight you have forward of the handgrip ( including closer to the hand grip ) the more nimble it will feel.

So the barrel and FF tube , as well as the gas block can dramatically alter a AR's "feel".

You don't need exotic parts just lighter than normal.

My 14.5 BCM ELW Fluted is VERY nimble.
 
I find that if it's too light up front, then the gun 'feels' nimble but is actually harder to shoot offhand than a gun with better balance and a bit of weight up front. I'd rather have the balance be neutral to front heavy than not.
 
why not just fill a balloon with helium and tie it to your carry handle? makes about as much sense as some of the other things people do to their ARs to make them ridiculously light
Click to expand...

Love it! A derigibAR, the HindenburgAR (trademark of LaRue Tactical...probably)

TCB
 
Faxon has a midlength 16" super light weight melonite barrel and light weight low profile gas block for under $200. I also found a neat titanium muzzle brake that weighs nothing, add a 12" ALG rail and you have a really light upper.
 
hard question, justin. i'd vote barrel, as the obvious #1 culprit. but 2nd place is more difficult as the lightest weight handguards are also ridiculously priced. so i'd probably guess MFT for that.

guess it's been 2 years since my last build... http://www.thehighroad.org/showthread.php?t=761427 that one is 5 lb 6 oz and didn't break the bank. i have some of the weight savings for magnesium aluminum components in the OP
 
I recently built a 5lb 16" 300blk

The two weight savers that stood out for my build was the aluminum bolt carrier and the monolithic cav15 poly lower.

These save right at a lb by themselves not because of the lower so much as the stock, buffer tube, and castle nut all being poly and integral
 
I went with a medium contour (because I couldn't find a light weight in stock) 10.5" barrel, with a spaced and welded 5.5" muzzle device. 9" generic Key mod free float handguard, all mounted to a BCM M4 upper. I could have gone with an upper that didn't have the forward assist or dust cover, but again I got what was in stock. A set of polymer flip sights, a no frills basic charging handle and a semi auto BCG round out the upper.

For the lower, I used a factory ATI Omni gen I complete lower. It weighs in just a hair under 6 pounds unloaded. I could possibly shave off a few ounces by going with a slick side upper, milled out BCG and half a dozen other things people do to shave weight. But I like the current weight and balance of the rifle, and with a 20 round aluminum GI mag, it's still under 6.5#. Nice little light weight rig.
 
Status
Not open for further replies.

Similar threads

Thompsoncustom
  • Locked
How to build a lightweight ar15.
Replies
22
Views
3K
BrocLuno
BrocLuno
Zak Smith
  • Locked
New Lightweight AR15 upper build
Replies
16
Views
1K
Zak Smith
Zak Smith
M
  • Locked
LR-308 Lightweight Build Questions
Replies
3
Views
645
matai
M
BSA1
  • Locked
What is considered to be a lightweight AR?
2 3
Replies
54
Views
13K
RogueNathan
RogueNathan
A
  • Locked
School me on light weight bolt carriers
Replies
3
Views
541
taliv
T
Back
Top