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Thread: "Precision" Build Questions...

  1. #1
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    "Precision" Build Questions...

    Gents-
    Ive been gathering parts for sometime now to MY version of a 20" precision rifle. It will not be, nor is it intended to be a full blown Navy Seal-USMC Sniper-Ninja rifle...but instead be as accurate a rifle as I can afford, with MY selected parts, for MY shooting ability and AO.
    Intends for the gun are: coyotes, crows, chucks, SHTF/Property defense...ect.ect.
    Im not wanting some heavy assed rifle, but one easily portable and accurate with good ammo.
    Ill be using 69/77 IMI & other quality ammo of that ilk..not gonna be blasting away with range ammo in this one.
    So- Ive got questions, as follows-
    1. What are the recommended torque specs for barrel & muzzle device?
    2. What are the torque specs on a double set screw gas block & what type loc-tite to use there?
    3. For THIS rifle..would an adjustable gas block be better or not?
    4. About the only part Ive not decided on is the trigger. I was going to get a 3lb. Velocity, as Ive run a 4lb in my LMT for many years now & love it, but Im open to suggestions, especially on Geissele triggers.
    5.Thoughts on facing/squaring the upper receiver?
    6. ANY other tips/tricks or recommended things I need to know?
    Also- are torque specs different for precision guns & fighting guns?
    The obedient always think of themselves as virtuous rather than the cowards they really are.

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    4. About the only part Ive not decided on is the trigger. I was going to get a 3lb. Velocity, as Ive run a 4lb in my LMT for many years now & love it, but Im open to suggestions, especially on Geissele triggers.

    I'd take a look at the LaRue MBT.

    Do you have the barrel in hand? If not I'd take a look at this one: http://www.gmriflebarrel.com/gm-m20-...wylde-chamber/

    223 Wylde Chamber, 1:8 twist, 20" long, 416 stainless steel, weighs 2.20 lbs., Fluted, honed, button rifled, air gauged, stress relieved, passivated, bead blasted matte finish, Nickel Boron extension with M4 feed ramps, and has a rifle length gas block.

    I have this barrel and it shoots much better than I do.
    Patriotism means to stand by the country. It does not mean to stand by the President... - Theodore Roosevelt, Lincoln and Free Speech, Metropolitan Magazine, Volume 47, Number 6, May 1918.

    Every Communist must grasp the truth. Political power grows out of the barrel of a gun. Our principle is that the Party commands the gun, and the gun must never be allowed to command the Party Mao Zedong, 6 November, 1938 - speech to the Communist Patry of China's sixth Central Committee

  3. #3
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    I'd take a look at the LaRue MBT.
    I’m not knowledgeable enough to add a lot to this conversation, but the above statement is solid. My MBT-2S feels lighter than and at least as smooth as my Geissele SSA. My G2S is actually noticeably less smooth, despite supposedly being “essentially the same thing” as the SSA. This is not criticism of the SSA; it is outstanding. It’s also not a hardcore critique of the G2S, just my experience in the past month.

    I have the MBT-2S in my “precision-esque” carbine.

    1. A. Depends on guidance from your handguard manufacturer, I believe? Stock barrel nut: 30 ft-lbs B. 15-20 ft-lbs.
    2. A. Unsure. B. Red loctite is what I’ve read BCM uses, from ‘those in the know’ on this forum.
    3. Not an expert. But...I wouldn’t think so. The 20” rifle length gas system is the basis for the whole system.
    4. See above.
    5. I looked at doing this with a build I had planned, but it was not going to be practical with the quality tools I would use. Essentially, using the Brownells lapping tool, for instance, didn’t seen to have a proven value and could potentially be detrimental. This was just my conclusion.
    6. I’m still a new guy.
    “God doesn’t need your good works, but your neighbor does.” - Luther

    Quote Originally Posted by 1168
    7.5” is the Ed Hardy of barrel lengths.

  4. #4
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    Thank you both for answers thus far. 26 INF..yes, got a barrel already..Criterion 20" Hybrid in Nitride finish. I will investigate that Larue, thank you.
    The obedient always think of themselves as virtuous rather than the cowards they really are.

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    1. Barrel nut and muzzle device should be to manufacturers specs I would think. I was told by a former AMU gunsmith that the muzzle devices they used were threaded until contact and Loctited in place.
    2. I only use pinned GB’s but I would just use Rocksett instead of Loctite
    3. I’ve never used an adjustable GB, I prefer to tune gas systems accordingly
    4. I use a SSA-E and love it. I also have a MBT and it is very nice. Closer in performance to the SSA-E than SSA IMO
    5. No idea

    Criterion makes a nice barrel. I enjoy mine, it is indeed very accurate. I’m going to replace it with a 20” Bartlein from Compass Lake for the velocity gains for long range predator hunting (currently using a 16”)

  6. #6
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    Quote Originally Posted by gunnerblue View Post
    1. Barrel nut and muzzle device should be to manufacturers specs I would think. I was told by a former AMU gunsmith that the muzzle devices they used were threaded until contact and Loctited in place.
    2. I only use pinned GB’s but I would just use Rocksett instead of Loctite
    3. I’ve never used an adjustable GB, I prefer to tune gas systems accordingly
    4. I use a SSA-E and love it. I also have a MBT and it is very nice. Closer in performance to the SSA-E than SSA IMO
    5. No idea

    Criterion makes a nice barrel. I enjoy mine, it is indeed very accurate. I’m going to replace it with a 20” Bartlein from Compass Lake for the velocity gains for long range predator hunting (currently using a 16”)
    You goin with the progressive rifling?
    The obedient always think of themselves as virtuous rather than the cowards they really are.

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    Quote Originally Posted by Straight Shooter View Post
    6. ANY other tips/tricks or recommended things I need to know?
    There are some tricks used by guys who build match grade service rifle uppers, but they may or may not be worth your time or of interest to you.

    Joe Carlos is a retired US Army MSG who served as an armorer for the Army Reserve Marksmanship Team. He claims that in his experience, shimming and gluing a barrel into an upper will reduce group size by as much as 1/3:

    https://www.youtube.com/watch?v=pJL-...efHKg&index=35



    (There are several more videos in that series with him, but the above it the most to-the-point about accurizing an upper by improving the fit between the barrel and receiver extension).

    You could probably approach the press fit he talks about by using an upper that in manufactured to have a tighter than normal fit to begin with, as are BCM forged uppers IIRC.

    Another short and less helpful video covering the same thing:

    https://www.youtube.com/watch?v=y-jKERY7KJE

    Criterion also recommends gluing their barrels in during installation:

    https://www.youtube.com/watch?v=XHxU...efHKg&index=28

    Again, maybe not for you, but it is something that some folks are doing.

  8. #8
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    I was going to suggest the MBT as well.


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    Quote Originally Posted by Straight Shooter View Post
    You goin with the progressive rifling?


    Unknown as of now

  10. #10
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    Several years back, C4IGrant did a rather accurate assembly using a BCM 410 SS barrel and a DD lite rail I believe. He mentioned that 40 ft lbs torque on the barrel nut was preferred for accuracy.

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