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First AR build, questions:

Discussion in 'Rifle Country' started by gunnutery, Oct 14, 2013.

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  1. gunnutery

    gunnutery Member

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    Ar15 build questions

    I've never really been an AR guy, but I do recognize the ARs abilities, as well as being more economically friendly, which is exactly what I'm looking for, a fun winter gun project that's mostly within my "budget."

    My basic overall goal is to have a short entry stock, flat top for future optic, free float forearm that covers most of the barrel. I'm not real picky on who manufactures the parts, like I said "economically friendly."

    I'm mostly looking at buying or trading into a complete upper.

    With that said, onto the questions:
    1) if I buy an upper barrel assembly with a standard front sight post, is it fairly simple to change it to a low profile gas block?

    2) If I buy an upper with a low profile gas block with a handguard retainer, does the retainer remove from the gas block easilly (or at all)?

    3) Ive been finding some sites with various parts for sale, but is there kind of a catch-all website that you recommend that has pretty reasonable prices?

    4) I googled this but I just want to clarify, I can run a 20" upper on a carbine size buffer and buffer tube and spring correct?
     
  2. goon

    goon Member

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    You may need to replace the buffer to get a 20 upper to run on a carbine lower, but that's a one-minute swap if you do. Buffers aren't expensive.

    I'd suggest you check out PSA. They're selling some pretty inexpensive stuff but their uppers are using FN barrels. They've got different stuff on sale every day and their inventory constantly changes, so save your pennies and buy when they have what you want in stock.
     
  3. JoeMal

    JoeMal Member

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    If you buy a FSP and want it removed to give yourself a longer rail..you may want to look into 'chopping' or 'shaving' it. This removes the top triangle "sight" component and leaves you with a factory-pinned, low profile gas block. A lot of folks actually recommend this over a an actual low-pro you would do yourself. This job can be done in as little as 15 minutes if you have the tools (hacksaw, grinder, or dremel are all tools I've seen used for this) Google it and you'll find tons of tips, videos, etc

    Brownells seems to be a good site that sells a ton of bits and pieces you may not find at other stores or websites. I would start there. If the retainer you're thinking of, is what I think it is, they can be removed with tin snips, vice grips, a dremel, and a little elbow grease.

    Agreed with what goon said...they are getting high marks for fair prices if you want to buy complete. I understand there's a little self pride with a DIY setup
     
  4. gunnutery

    gunnutery Member

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    Thanks a bunch guys! I checked out PSA, which I've heard of, but that's what I've been looking for.

    Chopping the FSP is a great idea, I'll do that if it comes to it.

    One more question.
    Does the 1:9 twist support heavier bullets? If so, does it still do okay with 55gr? I'll probably stick with the 55gr so should I look for 1:9 or 1:7?
     
  5. cfullgraf

    cfullgraf Member

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    Either twist rate will work fine with 55 grain bullets. A 1 in 7 twist barrel may not shoot the light weight bullets, like 40 grain, very well. They may disintegrate in flight due to over spinning.

    Some 1 in 9 twist barrels will shoot 68 and 69 grain bullets fine, some will not. Both should do fine with 60-65 grain bullets. A 1 in 9 twist barrel probably will not stabilize 77 grain and heavier bullets.

    I would probably go with the 1 in 9 twist. It is a good, all around twist rate for an AR.

    Hope this helps.
     
  6. mljdeckard

    mljdeckard Member

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    Order the free Brownell's AR parts catalog. All kinds of stuff you never knew you needed until you saw it in there.
     
  7. goon

    goon Member

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    Good God... I could dump a fortune at Brownells.
     
  8. ugaarguy

    ugaarguy Moderator Staff Member

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    It depends on how tight the pins are. If I wanted a low profile gas block, I'd just (carefully) cut off the A-frame and cold blue the steel to turn it into a low profile gas block. Pinned blocks are sturdier than set screw secured blocks, and most factory pinned blocks are on there pretty tight. Most scopes focus right past them at about 2.5-3x magnification and up, and many folks co-witness low magnification / zero magnification sights with the irons. You have lots of options, so don't worry too much about the gas block / FSB thing.
    Well, the gas block holds the retainer against a shoulder on the bbl, so not easily. Again, there's always the option to use the dreaded rotary tool and cut the retainer down.
    PSA, Brownells, and Midway USA are all pretty good places to look.
    Yep, but it shifts the point of balance forward, and they feel funny compared to a regular AR rifle or carbine - if you're used to those. Our neighbours to the north even run this as a standard issue rifle in the form of their Colt Canada C7A2. The one in the pic below is missing the triad rail under the A-Frame.

    800px-Canadian_C7A2_Rifle.jpg
     
  9. MachIVshooter

    MachIVshooter Member

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    Ugaarguy answered your questions pretty well, but I'll attack them a little, too.

    As mentioned, the factory front sight is pinned, and those pins can be VERY tight (I broke three punches and got a piece of shrapnel in my arm trying to get the sight off a DSA 16" middy. I did eventually win that fight, though). Generally, though, a decent hammer, a decent punch and either two guys or a guy with a good soft jawed vice can get the pins out pretty easily, and then it's just a little wiggling and the sight slides forward.

    Recommendation: put masking or electrical tape on the barrel forward of the sight to avoid marring the finish while removing it.

    Some low profile blocks use pins, many use set screws (grub screws). Pins are stronger, but I've never had one twist or work its way forward with thread locker on the set screws and as much torque as you can apply without stripping them.

    As said, you either have to remove the gas block or grind away the retainer.

    In addition to the aforementioned, DSA is very reasonable, but their stock can be problematic. Honestly, with the fluxing of stock from pretty much all manufacturers/distributors, a search engine is your friend. Amazon actually carries a ton of AR parts and often has free shipping, just no BCGs, receivers or barrels. Lots on eBay, too.

    As said, you will probably need to change the buffer (start at about $15), but otherwise it'll be fine.

    cfullgraf was pretty on-the-money, but I'll elaborate a little. While centrifugul force can cause bullets to self-destruct in mid air if the RPM is too high, the .223 from a 20" or shorter barrel just doesn't reach those velocities, so you'd be fine with a 1:7 and 40, 50 grain bullets (unless you try to use thinly jacketed .22 Hornet bullets). A 1:9 will reliably stabilize bullets up to 62 grain, but over that it can get iffy, and will depend on the specific bullet. Over 80 grains just isn't likely to stabilize in 1:9.

    Some manufacturers have split the difference; my 12.5" BCM stainless is 1:8. I honestly can't tell you how it performs with bullets over 62 grains, though, as I've never tried them in that rifle.
     
  10. LebbenB

    LebbenB Member

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    Actually, 1:8 is probably the best all-round twist rate for an AR, giving the user the broadest selection of bullet weights.
     
  11. wally

    wally Member

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    Also note, if they are mil-spec they are taper pins which means they need to be driven out from the "small" end towards the "big" end. The small and big are not very far apart in diameter. Some penetrating oil on them the day before helps a lot.


    If you want to add a free-float tube any FSB or gas block needs to be removed and reinstalled. Might be best to get a free-floated upper from the get go, or go stripped upper and buy only the parts you want for an even larger winter project. The few special tools you'll need will be basically paid for by not buying parts you will be discarding latter.
     
  12. gunnutery

    gunnutery Member

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    You've all been very helpful and Johny-on-the-spot for my questions. I've worked some with ARs and mantain the ones for our department, but it was some of the more scientific Qs that I knew you all could point me straight.

    I just saw some recent prices from DSA uppers and I'll probably go that route and alter what I need to after I get the othe parts, that way I have a functional affordable gun until I can afford the extras.
     
  13. ugaarguy

    ugaarguy Moderator Staff Member

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    Actually there are several free-float fore-ends from Midwest Industries, Daniel Defense, Troy, and others that clamp to the stock bbl nut.
     
  14. JoeMal

    JoeMal Member

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    This is correct. Centurion also makes a 'C4' rail that's a 2-piece free float rail. I'm waiting to find the right price on a used one for my current build.
     
  15. MachIVshooter

    MachIVshooter Member

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    DSA offers an amazing value; excellent quality at very reasonable prices. The only problem with that is that they have been perpetually unable to keep up with demand.

    The $265 16" fluted middy I ordered for my buddy was beautiful when it showed up this past May. Would have been nice to have got it in the same month I ordered, though...which was October 2012.
     
  16. justice06rr

    justice06rr Member

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    I would second that warning that DSA has some terrible shipping times. My roomate ordered some parts from them and it took a couple of months to arrive.

    You would be better served ordering parts from Palmetto, Brownells, Aimsurplus, and Midway. Don't forget you'll need to order tools like an AR15 wrench, vice blocks, punch set, etc if you don't already have those.
     
  17. gunnutery

    gunnutery Member

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    Thanks for the heads up, I saw on their website some uppers in the "ready to ship" scroll bar, so they're either caught up on demand or I just happened to see it right after a recent batch.

    One more quick question:

    Of the available lower parts kits, which one in the $70-80 range has the best trigger, or all they pretty much all the same in that price range? The ones I've seen listed have been CMMG, DPMS, RGuns and some others I've never heard of. As mentioned, Im not real picky on the brand, I've shot some RRA triggers and loved them, but I'm not able to dump a bunch of cash into the build currently, perhaps over time I'd upgrade.
     
  18. MachIVshooter

    MachIVshooter Member

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    Call them first. They are very helpful on the phone, I'll give them that.

    Who knows, they may actually have some ready to go. But at beginning of summer when I asked, I was told 8-12 months.
     
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