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Thread: A1 Upper with 6920 barrel assembly?

  1. #1
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    A1 Upper with 6920 barrel assembly?

    Planning a project of using an A1 Upper, A2 Lower and 6920 barrel assembly. It's going to be my semi-auto version of a Colt 723, all Colt parts laying around. Regarding the 6920 barrel and it's F Marked sight tower, refresh my memory - will I have to crank the front sight post all the way down to achieve zero or is it the opposite?
    Maj. USAR (Ret) 160th SOAR, 2/17 CAV
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    Black Mesa Ranch. Raising Fine Cattle and Horses in San Miguel County since 1879

  2. #2
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    Quote Originally Posted by OH58D View Post
    Planning a project of using an A1 Upper, A2 Lower and 6920 barrel assembly. It's going to be my semi-auto version of a Colt 723, all Colt parts laying around. Regarding the 6920 barrel and it's F Marked sight tower, refresh my memory - will I have to crank the front sight post all the way down to achieve zero or is it the opposite?
    Are you talking about a C7 type upper or an actual A1 upper? The C7 type upper has the Brunton Bump (brass deflector). If you are planning on using a C7 type upper, then it would be correct for a late model 723. In regard to the barrel, the late model 723 used a 14.5" barrel with M203 cuts. These were also built with using A1 and the later A2 profile lower receivers.

    Here is my late 723 I built. It has a Colt 14.5" barrel with a p&w ext. A2 FH. The upper is also Colt.



    Here is a reference link that may assist you.

    https://imageevent.com/willyp/firear...l723carbine556
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  3. #3
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    Quote Originally Posted by OH58D View Post
    Planning a project of using an A1 Upper, A2 Lower and 6920 barrel assembly. It's going to be my semi-auto version of a Colt 723, all Colt parts laying around. Regarding the 6920 barrel and it's F Marked sight tower, refresh my memory - will I have to crank the front sight post all the way down to achieve zero or is it the opposite?


    A 6920 barrel came from the factory with the correct front sight post and front sight triangle to be used in any carbine configuration, regardless of the rear sight configuration of the upper.

    An actual 723 would have came with a non F marked front sight triangle with a taller front sight post used on 600 and 700 series carbines.
    Last edited by scottryan; 11-11-19 at 15:40.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  4. #4
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    Quote Originally Posted by scottryan View Post
    A 6920 barrel came from the factory with the correct front sight post and front sight triangle to be used in any carbine configuration, regardless of the rear sight configuration of the upper.

    An actual 723 would have came with a non F marked front sight triangle with a taller front sight post used on 600 and 700 series carbines.
    So, an old A1 upper using a .40 inch higher shelf F Marked 6920 barrel (and keeping the same front sight post), I would need to lower that post? I know we're dealing with very small measurements, I just want to be able to zero the weapon without any parts changes.
    Maj. USAR (Ret) 160th SOAR, 2/17 CAV
    NRA Life Member
    Black Mesa Ranch. Raising Fine Cattle and Horses in San Miguel County since 1879

  5. #5
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    Quote Originally Posted by OH58D View Post
    So, an old A1 upper using a .40 inch higher shelf F Marked 6920 barrel (and keeping the same front sight post), I would need to lower that post? I know we're dealing with very small measurements, I just want to be able to zero the weapon without any parts changes.


    No

    A 600/700 carbine barrel with regular FSB and taller post is the same overall dimension as a 6920 barrel with F marked FSB and regular post.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  6. #6
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    Quote Originally Posted by scottryan View Post
    No

    A 600/700 carbine barrel with regular FSB and taller post is the same overall dimension as a 6920 barrel with F marked FSB and regular post.
    Since I haven't done the measurements, this is good to know. FYI the upper is a 1980's vintage 733 C7 A1 with the shell deflector.
    Last edited by OH58D; 11-16-19 at 23:06.
    Maj. USAR (Ret) 160th SOAR, 2/17 CAV
    NRA Life Member
    Black Mesa Ranch. Raising Fine Cattle and Horses in San Miguel County since 1879

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