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Been meaning to build a lightweight AR15 for a few years now, primarily due to complaints from new female shooters. The more I think about it, I can see how a lightweight build would appeal to everyone, myself included. Budget constraints won't allow for the lightest build, but we should be able to get close.

PARTS ACQUIRED

BARREL:
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LOWER RECEIVER: Northwest Firearms Stripped Lower
TRIGGER / LPK: Palmetto State Armory MOE LPK
STOCK: MFT Battlelink Minimalist
OPTIC: Burris Fast Fire 3
 
If you're looking to shed ounces, look at V7 weapon systems.

Thanks for the tip, I'll check em out. I'm still getting a feel for where I should skimp, where I should splurge, and what I can't afford. Seems the sky is the limit when it comes to the cost of lightweight stuff.

My plan right now is to get it put together within my budget, then install nicer/lighter components as I can afford them.
 
How light do you want to go. I wanted a lighter weight rifle so I went with the DEL-Ton DT Sport. It only weighs 5.8 pounds. Much nicer that my seven and a half pound Ruger.

To be honest, I have no clue. I've never held a 'lightweight AR', so I don't necessarily have a weight goal. I'm pretty sure I'll actually enjoy the build more this way, making it progressively lighter. I'm also learning a ton about the platform as I research different components. For example, I'm still not sure if I want to sacrifice the forward assist and dust cover for weight. I don't know how to properly use the forward assist nor under which conditions a dust cover is a good idea, but I'm looking forward to learning about both. My knowledge about the AR platform is laughable, but not for long :)
 
I ended up doing a lightweight build last year. It ended tipping the scales at 5lbs 6oz. I saved the majority of the weight in 3 areas; the barrel 16" BCM light weight enhance fluted barrel (one could go lighter with 14.5" if you wanted a pinned flasherhider). The BCG saved more weight by getting a skeletonize carrier, there are titanium BCG out there that will saved an additional.5oz but for $200 more! Lastly the real weight savings was on the stock Mission First Minimalist stock. I did tossed in some V7 parts like a Ti gas block, Ti A2 flash hider, Ti take down pins and aluminum forward assist. I also used a 15" Daniel Defense slim key mod hand guard.

Total cost for the rifle was just a touch over $700

There are a couple things that I would change, strike industries light wight port door and BMC KMR rail shorter than the 15" currently install.
 
IMHO its better to keep the forward assist and dust cover. Its still possible to get under 7 lbs with them there.

Asid from what you listed, a slim keymod rail helps shave weight.
 
I ended up doing a lightweight build last year. It ended tipping the scales at 5lbs 6oz. I saved the majority of the weight in 3 areas; the barrel 16" BCM light weight enhance fluted barrel (one could go lighter with 14.5" if you wanted a pinned flasherhider). The BCG saved more weight by getting a skeletonize carrier, there are titanium BCG out there that will saved an additional.5oz but for $200 more! Lastly the real weight savings was on the stock Mission First Minimalist stock. I did tossed in some V7 parts like a Ti gas block, Ti A2 flash hider, Ti take down pins and aluminum forward assist. I also used a 15" Daniel Defense slim key mod hand guard.

Total cost for the rifle was just a touch over $700

There are a couple things that I would change, strike industries light wight port door and BMC KMR rail shorter than the 15" currently install.

5lbs 6oz for $700 sounds like a good deal! Any photos? That BCM barrel looks nice. The barrel was one place I figured I should splurge, and I've heard great things about the Faxon (it's around 19 oz). I also wanted to go with a 16" vs a 14.5" so I didn't have to pin it. Which carrier did you go with? I haven't dug into the titanium stuff yet, but it seems a guy could spend hundreds to shave a couple of ounces. Definitely not worth it to me, I'm not competing with anyone for the lightest build. When looking at stocks I also chose the MFT minimalist. Best part was it was only $33! I'm looking at handguards now, figuring out which lengths go with which gas systems.

IMHO its better to keep the forward assist and dust cover. Its still possible to get under 7 lbs with them there.

Asid from what you listed, a slim keymod rail helps shave weight.

This is what I was figuring, I think I'd rather have them. Definitely planning on going with a free floating rail.

5.85 pounds, Carbon Fiber by Windham Weaponry

Man, that seems like a fantastic deal for a lightweight AR. This will be a Northwest Firearms build, so I'll be using one of our lowers.
 
I'll have get some pix later, the BCG I used is the nickle boron lightweight from AIM Suplus
Light Weight AIM AR .223/5.56 NiB 9310 MPI Bolt Carrier Group

If I would have had a plan of what I was going to build I would have purchase different upper and lowers, I had a set of receivers and just went from there. The rifle works great and young kids love it's weight. I'll try to post some pix later this week

That's the one I was thinking of getting, if/when it comes back in stock. Seems to be the best value for a lightweight BCG.

Do not be afraid to drill holes:D

This is exactly what I don't want to do! :D

I can't believe the extremes some go to for a few ounces (or pounds in some cases). I don't want to sacrifice form or reliability. Won't be a contender for lightest AR, but that isn't what I'm after :)
 

Keep in mind you will need a riser for this sight, mounting this directly to your upper will make it too low.

If you're looking to shed ounces, look at V7 weapon systems.

V7 makes quality Ti stuff, but it is very expensive to shed very little weight. Thinks like Ti takedown and pivot pins, gas block, castle nut, selector, etc.

The BCG saved more weight by getting a skeletonize carrier, there are titanium BCG out there that will saved an additional.5oz but for $200 more!

A LW BCG is the last thing I'd do on any AR for serious use, if it is a gamer, whatever, do what you want. Here is what one of the original designers of the AR-15 has to say on the subject. Go to the 5:00 min mark and more specifically at 6:25 min.

5.85 pounds, Carbon Fiber by Windham Weaponry

I wouldn't own that piece of sh!t if you gave it to me.

I'll have get some pix later, the BCG I used is the nickle boron lightweight from AIM Suplus
Light Weight AIM AR .223/5.56 NiB 9310 MPI Bolt Carrier Group

Same thing here on the LW BCG. Also, stick with a standard MilSpec Phosphate finish on your BCG, if must have a Gucci finish make it NP3. NP3 VS. Nickel Boron They are available from SIONICS

The best places to shave weight on an AR is the barrel profile, stock and handguard plus no FSB, no carry handle.
 
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IMG_0156.JPG It's a plane rifle but it was a fun build.
I do have other AR15 built for "serious" use, but so far this rifle has been 100% reliable with all kinds of shooters and I don't think I would be concerned if this was my only rifle.
 
View attachment 329099 It's a plane rifle but it was a fun build.
I do have other AR15 built for "serious" use, but so far this rifle has been 100% reliable with all kinds of shooters and I don't think I would be concerned if this was my only rifle.

That's a good looking rifle! If I can get somewhere around 5lbs with no reliability issues I'll be a happy camper :)

I spent more time than I should have today researching various component of this build. I wouldn't be surprised if lightweight builds are among the most research-intensive. I might have also weighed the mil-spec parts of a PSA lower build kit I have laying around for comparison purposes :s0092::s0112:

I can't believe the increased costs for such small weight differences. I don't have the bankroll to get stupid with this build.
 
That's a good looking rifle! If I can get somewhere around 5lbs with no reliability issues I'll be a happy camper :)

I spent more time than I should have today researching various component of this build. I wouldn't be surprised if lightweight builds are among the most research-intensive. I might have also weighed the mil-spec parts of a PSA lower build kit I have laying around for comparison purposes :s0092::s0112:

I can't believe the increased costs for such small weight differences. I don't have the bankroll to get stupid with this build.
If you check this thread Lightweight AR Picture Thread - AR15.COM you can find all kinds of things people have done to achieve their lightweight builds.

The Ti parts that make the most difference in the rifles balance is the gas block and flash hider. That saved an ounce or two out at the end of the rifle. Yeah one could get aluminum gas blocks verses the Ti gas block for less but I'm not sure that's the correct material for that purpose. More than anything it was a fun build.
 
View attachment 329099 It's a plane rifle but it was a fun build.
I do have other AR15 built for "serious" use, but so far this rifle has been 100% reliable with all kinds of shooters and I don't think I would be concerned if this was my only rifle.

How many rounds of what kind of ammo?

BCM KMR *ALPHA* 7 (KeyMod™ Free Float Handguard)
Here's one handguard to look at if going for a free float handguard.

The KMR non-alpha is even lighter if you can find one (most likely on the used market), but you'll want a longer handguard that 7" if you are using a mid-length gas system with a lo-pro gas block. The 7" is made to fit behind the standard FSB on a carbine, 9" is made to fit behind the FSB on a middy. You want a minimum 10" for a lo-pro gas block, it will still stick out of the rail. Go with a 13" or longer if want the gas block completely under the handguard, obviously the longer you go the weight up front you'll get.
 
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BCM KMR *ALPHA* 7 (KeyMod™ Free Float Handguard)
Here's one handguard to look at if going for a free float handguard.

I really like those, but they're expensive and KeyMod only (I have all M-LOK stuff right now). These two are at the top of my list at the moment.

$100 - 7.85 oz - Ergonomic Modular Rail (EMR) V1 M-LOK
$90 - 7.7 oz - 12" ULTRA SLIMLINE OCTAGONAL 5 SIDED M-LOK FREE FLOATING HANDGUARD WITH MONOLITHIC TOP RAIL

How many rounds of what kind of ammo?



The KMR non-alpha is even lighter if you can find one (most likely on the used market), but you'll want a longer handguard that 7" if you are using a mid-length gas system with a lo-pro gas block. The 7" is made to fit behind the standard FSB on a carbine, 9" is made to fit behind the FSB on a middy. You want a minimum 10" for a lo-pro gas block, it will still stick out of the rail. Go with a 13" or longer if want the gas block completely under the handguard, obviously the longer you go the weight up front you'll get.

Great info to have, I've been trying to figure out which length I should go with. I do want the gas block covered.
 

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