Quantcast
  1. Upgrade efforts paused for now. Thanks for your patience. More details in the thread in Tech Support for those who are interested.
    Dismiss Notice

AR-15 Weight Loss Program! Getting there, but I need more!

Discussion in 'Rifle Country' started by coloradokevin, Feb 10, 2018.

Thread Status:
Not open for further replies.
  1. coloradokevin

    coloradokevin Member

    Joined:
    Mar 22, 2008
    Messages:
    3,279
    I have been piecing together a lightweight AR-15 build for a while now, and I finally weighed the rifle last night. I built this off of an 80% lower, and I plan to Cerakote the bare upper receiver when I finish piecing everything together.

    The good news is that this thing is light; the lightest I've ever built. It tips the scales at a mere 4.296 pounds (68.7 ounces). The bad news is that I was targeting a build of less than 4 pounds.

    Here's where I've saved weight so far:

    1) Pencil barrel
    2) lightweight steel BCG
    3) Ultralight carbon fiber hand guard (seriously the lightest one I think is made).
    4) Ultralight carbon fiber buffer tube/stock (again, the lightest I could find).
    5) Ultralight Taccom buffer.
    6) Ultralight backplate.
    7) Ultralight castle nut.

    My goal was to come in at less than 64 ounces, so I'm 4.7 ounces overweight at the moment. I also don't have the forward assist or dust cover installed at the moment, though I'm thinking of a forward assist plug, and a lightweight dust cover. I will also add that I elected to use a 16" barrel, rather than a shorter barrel with a pinned muzzle device.


    While I may or may not do anything else to this rifle, where would you look to shave weight at this point, if you were trying to do so? I worry that further decreases in weight might come with substantial decreases in reliability or durability, and will only arrive at significant additional cost. I originally set out to build this rifle with the goal of making a lightweight rifle my wife would enjoy (she's 105 pounds). But, the addiction of going lighter took hold, and the goal of breaking 4 pounds is strong. NOTE: I know there is no need to go lighter, it's really just a goal I'm exploring here, as a proof of concept!



    Here are my ideas, and my reservations on each of these:

    1) I could go with an aluminum BCG, and that would probably make up most of the difference between my goal and my current weight. But, aluminum BCG's aren't known for reliability or longevity.

    2) I could save maybe an ounce with an ultralight compensator in place of the A2 flash hider. No real downfall here other than $$$.

    3) I could go with an ultralight gas block, though the adjustable gas block I am currently using is pretty darn light, and adjustability is something I consider pretty necessary with the low mass BCG and low mass buffer.

    4) I could buy ultralight hardware for the lower. However, this stuff is really expensive for a marginal savings in weight.

    5) I could go with a lightweight receiver set, instead of a standard receiver set. This might save the most weight, but with potentially a great increase in cost, an inability to use the receiver I milled myself, and potential durability issues (I've heard of magnesium receivers cracking, and can't even find those for sale these days, and I've heard plenty of problems with polymer receivers).

    6) I could start drilling or cutting pieces from the receiver for weight savings. I worry that this would look like a hack-job, because I don't have CNC equipment to do this! Also, I'm not sure how much weight I could save without compromising strength on critical components.


    Anyway, the attached pictures show the rifle as it currently sits. And, no, I didn't design it to match the trash can... that just happened by accident! And, normally the wife looks a lot happier, except when I drag her away from writing an e-mail to hold a rifle for a picture (she'd kill me if she knew I was posting it anyway). The upper will eventually be Cerakoted to either match the lower, or change the entire color of the finished rifle.

    IMG_1941.jpg IMG_1947.jpg
     
    Armored farmer and chicharrones like this.
  2. Browning

    Browning Member

    Joined:
    Mar 21, 2007
    Messages:
    2,927
    Location:
    North TX
    Well...those last 4.7 ounces are going to cost you. Are you sure it's worth it? Seems like you already have some pretty good weight savings. Really ultra lightweight carbines are known for not being all that steady on target.

    If you decide to do it how much does your BCG weigh now?

    There are these from JP Enterprise. I'm pretty sure they'd back their product if something happened to it. Might want to check about a warranty just in case.

    https://jprifles.com/buy.php?item=JPBC-1

    They're 3.76 oz. with key installed.

    Personally I wouldn't change that adjustable gas block or start drilling holes in it to save weight. I think the ability to adjust your gas is worth the macro ounces that you might save and unless you're an artist with a drill I agree that holes would look like a hack job.
     
    coloradokevin likes this.
  3. WestKentucky

    WestKentucky Member

    Joined:
    Feb 1, 2014
    Messages:
    12,279
    Location:
    Middle Tn
    Skeletonize the lower. Theres a lot of useless mass in the magwell area and some weight to be saved on the grip and stock. Your really light with stock parts, now you need to put those stock parts on a diet. And I’m not sure if you would be comfortable doing it, but there is a lot of weight to lose in the lower where the material is not milled out for the FA portion of the trigger pocket. You can’t open that up from the top, but you could cut part of that weight out from other angles. Just make sure you don’t cut it out so far as to open up that pocket more than is legally advisable.
     
    coloradokevin likes this.
  4. coloradokevin

    coloradokevin Member

    Joined:
    Mar 22, 2008
    Messages:
    3,279
    My carrier looks to weigh 6.8 ounces according to the manufacturer, but that's minus the firing pin that is included in the JP offering. If I add the firing pin into the equation, I'm looking at 7.1 ounces for the carrier and pin. So, a move to that ultralight carrier would save me 3.34 ounces (give or take), and I could make up the other ounce in the muzzle device. Those to changed together would put me at just over 4.34 ounces of saved weight, which is very close to my goal. But, we're talking about an additional $500 to get there, unless I can find someone else offering an ultralight carrier for less (I saw one company online that had one, but they were sold out everywhere, which makes me wonder if they're still doing business).

    As for the "am I sure it's worth it" part of the equation... of course I'm not! LOL.

    At this point I realize that any additional weight savings is only there for bragging rights. The original intent was only to take some weight off of the front of the rifle so my wife would enjoy the practical weight of it more on the range (she hates trying to hold heavy rifles -- she's a small lady). Anyway, I got a bit carried away, then I set a real tough goal for myself of trying to say that I built a functional AR-15 that weighed 3.something pounds! I'm honestly not sure if I will do anything else, but I thought I should at least explore the options.
     
    adcoch1 likes this.
  5. coloradokevin

    coloradokevin Member

    Joined:
    Mar 22, 2008
    Messages:
    3,279
    Skeletonizing the lower was something I have been considering, I'm just not so sure that I could do it without making it look like too much of a hack-job. This is an 80% lower, so the original milling of the trigger group was done by me anyway. I know I could mill a bit more material out of the rear shelf area, because I almost accidentally did that when I forgot to put the pin in that prevents you from doing so. But, I worry that I'll compromise the strength of this area if I go too far, and I'm not sure how far I can go without doing so, or if the weight savings will be substantial enough to bother.

    I've also seen a lot of lowers with substantial amounts of material removed around the mag well area. That would probably save some weight, I just have to figure out how I can do it without looking like a three year old with a Sawzall built this rifle!
     
  6. WestKentucky

    WestKentucky Member

    Joined:
    Feb 1, 2014
    Messages:
    12,279
    Location:
    Middle Tn
    Just tape it off geometrically and go slow. Drill your corners to round them off nicely, then clean up your cuts when your done. It’s not so bad. Is that a poly lower?
     
    coloradokevin likes this.
  7. Hokie_PhD

    Hokie_PhD Member

    Joined:
    Jan 29, 2017
    Messages:
    2,734
    Location:
    Central Virginia
    What a pout going to a poly lower?
    Rural King had some on sale last month for less than $40. For that price it seems like it would be worth considering if they’re reliable enough for your needs.

    Also is that stock the lightest you can find? I have a Ace Skeleton stock on the AR I’m building. It wasn’t the lightest one I could find but it was pretty close. The lightest I could find was basically a buffer tube with a butt.
     
    coloradokevin likes this.
  8. coloradokevin

    coloradokevin Member

    Joined:
    Mar 22, 2008
    Messages:
    3,279
    No, this is a 7075 aluminum lower. I milled it was the Easy Jig Gen II jig, then Cerakoted it at home. It's a little oily in the picture, which I think gives it a plastic appearance.
     
    chicharrones likes this.
  9. coloradokevin

    coloradokevin Member

    Joined:
    Mar 22, 2008
    Messages:
    3,279
    This is also a buffer tube with a butt, all carbon except for the screw threads. It's made by a company called Smoke Composites, and it weighs 4.2 ounces total WITH the backplate and castle nut.

    $40 for a polymer lower isn't too bad. I'd need to get it to an FFL here (shipping cost and then a $15 transfer fee, and then pay the stupid Colorado background check fee of $15). So, in reality I'd probably spend more to get the darn thing than I would to buy it, but that's still a lot cheaper option than trying to shave weight on the BCG!
     
  10. Demi-human

    Demi-human maybe likes firearms a little bit…

    Joined:
    Dec 8, 2016
    Messages:
    5,743
    Location:
    The Haymarsh, MI (Aka, Paradise.)
    You need less!:)

    Do you need the Compensator?

    A receiver set, like the F-One, will net the most loss. To weight and wallet.;) I would also not coat it. That is of course if you can stand the shine. Everything adds up, even finish and lube.

    Mill out the grip too.
     
  11. adcoch1

    adcoch1 Member

    Joined:
    Oct 2, 2015
    Messages:
    3,368
    Location:
    Centralia Washington
    You could run it without a buffer. I made a washer plate with a conical center to locate the spring, then ran it without a buffer on a test in mine. With the adjustable gas block you should be able to dial it in that way.
     
  12. Hokie_PhD

    Hokie_PhD Member

    Joined:
    Jan 29, 2017
    Messages:
    2,734
    Location:
    Central Virginia
    I was about 15 minutes away from a Rural King. Virginia background check is currently $2. So as long as Dr Awful and the other anti gun loons elected in November don’t get their way it’ll stay that way. So here it’s the cost of the item, sales tax and the $2 fee.

    I’m currently about an hour away from the nearest Rural King. So it’s not so easy to just drop in and see what they have.

    When I saw the sale I was tempted to try one, but I picked up a few Anderson receivers when Primary Arms had them for $30. Since I still need to finish my current build and ultra light weight isn’t a concern I’ll wait unless they do a killer sale and I’m up that way. That said, if you go that route I’d love to hear how the poly lowers work
     
  13. someguy2800

    someguy2800 Member

    Joined:
    Sep 16, 2015
    Messages:
    7,553
    Location:
    Minnesota
    Take off the bird cage and put an aluminum thread protector on it. That would be good for 2 oz and it costs $10. How much does your barrel weigh? Beyond that I think I would look at a polymer lower. I don't think I personally would want any lighter of a carrier as I think reliability and durability will suffer. My father in law has a bushmaster carbon 15 that has been great, that is my only experience with polymer receivers. A slick side upper might be a couple ounces lighter too.
     
  14. coloradokevin

    coloradokevin Member

    Joined:
    Mar 22, 2008
    Messages:
    3,279
    I did consider a slick-side upper. Strangely, some that I looked at were just as heavy (or heavier) than the traditional style, and some didn't list weights. But, I'm sure that there are some lighter versions out there, somewhere.

    Maybe I will give the polymer lowers a try. I've never used one, but the investment isn't big to find out.
     
  15. WestKentucky

    WestKentucky Member

    Joined:
    Feb 1, 2014
    Messages:
    12,279
    Location:
    Middle Tn
    Poly lowers are ok if you don’t beat them up. If you do beat them up the rear of the lower reciever breaks off from he takedown pin hole at n angle down to just above the grip. I would definitely keep the aluminum and cut out extra weight on it
     
    chicharrones likes this.
  16. Browning

    Browning Member

    Joined:
    Mar 21, 2007
    Messages:
    2,927
    Location:
    North TX
    That would get you most of the way there then. It's just a bit costly (which is kinda what I meant with the 'is it worth it?' comment).

    If a poly lower is possible (I thought that this was a "Help me make it work with what I've gotten so far" thread) I'd go there first.
     
  17. chicharrones

    chicharrones needs more ammo

    Joined:
    Jan 19, 2010
    Messages:
    9,700
    Location:
    Galveston Bay is an Hour Away ©
    I vote for replacing the flash hider with a thread protector, skeleton-izing the existing lower, plugging the FA, and leaving the dust cover off.
     
    Last edited: Feb 10, 2018
  18. dh1633pm

    dh1633pm Contributing Member

    Joined:
    Apr 28, 2009
    Messages:
    4,436
    Location:
    Central New York
    Make sure the screws for the bolt handle and stock are no longer than needed for the job. Every grain counts when your saving ounces. The side of the receiver has the forward assist that your aren't using, you could loose that. Also is the grip as light as needed?
     
  19. IndianaBoy

    IndianaBoy Member

    Joined:
    Jan 3, 2005
    Messages:
    1,508
    Nice! I would probably call it good, but that is just me.
     
    chicharrones and Browning like this.
  20. someguy2800

    someguy2800 Member

    Joined:
    Sep 16, 2015
    Messages:
    7,553
    Location:
    Minnesota
    Oh and not to move the goal post but it's not a rifle until it has sights!
     
    chicharrones likes this.
  21. BSA1

    BSA1 member

    Joined:
    Apr 20, 2011
    Messages:
    7,492
    Location:
    West of the Big Muddy, East of the Rockies and Nor
    I am researching a light(er) build myself although not near as light as yours.

    First I would ditch the upper and go with a slick side from Anderson or PSA. Anderson has a brass deflector whereas the PSA does not. The PSA is listed at 6.0 oz.

    Second skeletonize the lower and upper like Jerry Miculek's.

    http://weaponsmedia.com/archives/6253

    I am not going for as radical as yours so I am using the Anderson slick side upper to avoid brass coming back at me and Mission First Tactical Minimalist stock.
     
    Last edited: Feb 11, 2018
    chicharrones likes this.
  22. zaitcev

    zaitcev Member

    Joined:
    Oct 14, 2016
    Messages:
    1,089
    Did you look at GWACS lower? I see your stock is not adjustable, so...
     
    Panzerschwein and Everready73 like this.
  23. greyling22

    greyling22 Member

    Joined:
    Aug 6, 2007
    Messages:
    6,638
    Location:
    East Texas
    Be careful buying an slick upper. I came across a web page indicating the slick uppers are heavier because they have thicker walls http://ar15armory.com/forums/topic/144225-is-physics-playing-a-trick-on-me-stripped-upper-weights/
    If i was looking to shave off a little additional weight, I'd lose the flash hider, and cut the hook off the hammer. maybe look at grinding down the safety selector some. Might also be able to shorten the grip screw. I don't think you will save a lot of weight cutting aluminum off the lower unless you go very aggressive with a mill.
     
    chicharrones likes this.
  24. Elkins45

    Elkins45 Member

    Joined:
    Dec 25, 2009
    Messages:
    6,408
    Location:
    Northern KY
    GWACS lower is the route I would go...in fact I did.

    Chasing those last few ounces is going to get really expensive. You have already passed the optimization point on the cost/benefit curve.
     
    Browning likes this.
  25. BSA1

    BSA1 member

    Joined:
    Apr 20, 2011
    Messages:
    7,492
    Location:
    West of the Big Muddy, East of the Rockies and Nor
    That may be true.

    Aero Precision lists their AR stripped upper with no forward assist but has lugs for ejection port cover as weighing 6.55 oz. Of course the ejection port cover and hinge pin will add to that weight if used.

    My research gives the weight of the Anderson stripped upper with brass deflector, no forward assist and no ejection port cover at 6.88 oz.

    PSA is still the lightest at 6.0 oz.

    Since we are talking about shaving fractions of Grams now removing metal from the lower and upper will help. As lowers are so inexpensive there is not a lot of money at stake. Whether it is practical and keeps the gun running reliably is a unanswered question.
     
    Last edited: Feb 11, 2018
Thread Status:
Not open for further replies.
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice