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Thread: Upper receiver options for precision build

  1. #1
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    Upper receiver options for precision build

    I asked this question on TOS but didnt get a lot of responses from those with first hand experience with these receivers.

    Im wanting to build an AR that is as accurate as I can make it. 18 223 wylde rifle length heavish profile barrel chambered by Craddock/Keystone/CLE on a Bartlein/Kreiger/Douglas blank (any thoughts on that would also be appreciated), geiselle or larue trigger, etc etc and will wear a suppressor 99.9% of the time.

    Originally I was looking at an Aero M4E1 receiver set as I figured the barrel nut being machined into the upper would make for a more rigid assembly as well as prevent handguard deflection from affecting the barrel. Im just not completely sold on Aero as a part supplier for this type of build.

    Ive seen the Seekins IRMT uppers which are the same concept as the Aero; not in love with the handguard options but Id deal with it if they are truly the best option. Also considering the Vltor MUR combined with a stout rail like a Geiselle. BCMs new mk2 upper also caught my eye, relatively untested at this point but I like my other BCM gear.

    What can the experts here tell me about the M4E1 set compared to the others listed above? Any other receivers I should be looking at?

    Thanks!

  2. #2
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    I have been happy with my MUR based uppers. I'm interested in what the thread turns up.

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    Vltor MUR is a great option. Little more expensive but you can find for around $150

    I would also look at SOLGW. They undersize the barrel extension slightly for a tight barrel fit (like BCM) which people say helps with accuracy. They also slightly oversize the lugs on the upper so you get a nice tight fit (instead of needing tension screw in lower) with their lower, or most others

    BCM also has a new upper out which should be more rigid that a standard milspec. They also undersize for tight barrel fit. If you are on a budget you can also pick up one of their normal blem uppers for under $70. I have bought several and like these

  4. #4
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    Mur, mega, new bcm receivers. The bcm will have the added advantage of needing to thermal fit the barrel eliminating the need for bedding via shims or loctite.

  5. #5
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    The MUR/ VIS and BCM Gen 2 should be what you are looking for. They are both forged, reinforced, and held to close (tight) spec. Most options which aren't traditional forged receivers are going to all be billet. Cross Machine Tool has a niece upper they make which is billet, and needs to be typically tapped into place or heated to allow the barrel extension to insert and seat.

    There are a lot of sloppy holed receivers out on the market. Some are notable for how loose they are, while others tend to be just a bit more on the "drop in" side. Much like yourself, I would prefer a tight fit when it comes to the receiver and barrel extension fit.
    Stick


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  6. #6
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    Well I ordered one of the BCM MK2 uppers. And an MUR.

    And some LPKs

    And some BCGs

    At least I'll be able to compare the two uppers visually side by side when they arrive. I may end up ordering an M4E1 upper/HG too just to avoid the "what if" thoughts.

    If ya'll want I'll post some side by side pics of the uppers. Perhaps this will slowly turn into a build thread.

    Now I need to decide on a lower....Spikes Viking, M4E1 and Noveske Gen 2 on hand

  7. #7
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    Good deal. Rail compatibility will come into play with certain rails.

    Now, the upper you choose is just part of the equation. Are you going to send the chosen upper to the barrel source and have a barrel extension selected to be tight inside the barrel extension? If not, are you going to shim or loctite the barrel extension for a tight fit? There is another thread that addresses these ideas.

    https://www.m4carbine.net/showthread...ess-Shim-Stock
    Last edited by taekwondopreacher; 01-11-20 at 07:24.

  8. #8
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    Off Topic:

    Stick, tell Paul and his Eggheads we want some BCM Fixed/PRS-style stocks, and some Mk2 18” SS URGs.

    Quote Originally Posted by Stickman View Post
    The MUR/ VIS and BCM Gen 2 should be what you are looking for. They are both forged, reinforced, and held to close (tight) spec. Most options which aren't traditional forged receivers are going to all be billet. Cross Machine Tool has a niece upper they make which is billet, and needs to be typically tapped into place or heated to allow the barrel extension to insert and seat.

    There are a lot of sloppy holed receivers out on the market. Some are notable for how loose they are, while others tend to be just a bit more on the "drop in" side. Much like yourself, I would prefer a tight fit when it comes to the receiver and barrel extension fit.

  9. #9
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    Quote Originally Posted by Outlander Systems View Post
    Off Topic:

    Stick, tell Paul and his Eggheads we want some BCM Fixed/PRS-style stocks, and some Mk2 18 SS URGs.
    Nobody wants these things. Hush.


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  10. #10
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    Quote Originally Posted by taekwondopreacher View Post
    Are you going to send the chosen upper to the barrel source and have a barrel extension selected to be tight inside the barrel extension?]
    I hadn't been planning on it but this seems like a reasonable idea so sure. I had been planning on bedding with loctite.

    I think I'm pretty much decided on a Bartlein barrel from Craddock, I imagine I can send the upper to him.

    Really the only thing I need to decide on now is a handguard. Geissele is still at the top of the list (in particular the mk14) but is there anything else I should be looking at that would create a more rigid interface between the HG/barrel nut/upper?


    Quote Originally Posted by Outlander Systems View Post
    Off Topic:

    Stick, tell Paul and his Eggheads we want some BCM Fixed/PRS-style stocks, and some Mk2 18” SS URGs.
    This build is getting a Magpul PRS stock, but if BCM had an alternative....

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