Page 1 of 4 123 ... LastLast
Results 1 to 10 of 36

Thread: 12.5 Midlength gasport

  1. #1
    Join Date
    Mar 2011
    Location
    Sweden
    Posts
    106
    Feedback Score
    5 (100%)

    12.5 Midlength gasport

    I’m building a 12.5 upper and for different reasons a chrome-lined midlength Faxxon barrel cut down from 16” to 12.5” is what I’m going to run. Gas port measures 0.075”. Gun will be used 50/50 supressed/unsupressed running M855 or similar duty grade brass cased ammo only. Gasport large enough to run it unsupressed? If not what size would you recommend? I have an adjustable gas block I could use to run different settings for suppressed/unsupressed if necessary. Any thoughts?

  2. #2
    Join Date
    Jun 2012
    Location
    northern CA
    Posts
    962
    Feedback Score
    2 (100%)
    I have a 14.5 BCM mid that im going to cut down to 12.5. I plan on leaving the gas port alone, and adjust if needed. Once you get it up and running report back here if you dont mind. I was going to send mine off last week but life decided I needed to spend money on other things. If I finish mine first I will let you know what I find.

  3. #3
    Join Date
    Mar 2011
    Location
    Sweden
    Posts
    106
    Feedback Score
    5 (100%)
    Quote Originally Posted by jstone View Post
    I have a 14.5 BCM mid that im going to cut down to 12.5. I plan on leaving the gas port alone, and adjust if needed. Once you get it up and running report back here if you dont mind. I was going to send mine off last week but life decided I needed to spend money on other things. If I finish mine first I will let you know what I find.
    Sure! FYI it might take me a 2-3 weeks to get everything together and conduct a proper testfire of a few hundred rounds. Looking forward to hearing about your findings aswell.

  4. #4
    Join Date
    Dec 2015
    Location
    Former USA
    Posts
    3,134
    Feedback Score
    0
    Triarc and Centurion do 12.5 mid. Don't recall the gas port size though.
    You won't outvote the corruption.
    Sic Semper Tyrannis

  5. #5
    Join Date
    Nov 2010
    Location
    MI
    Posts
    3,516
    Feedback Score
    22 (100%)
    The 12.5" MID configuration is best suited to a dedicated suppressed role.
    Black River Tactical
    BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
    BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
    BRT Bolt Carrier Groups M4A1, M16 CHROME
    BRT Covert Comps 5.56, 6X, 7.62

  6. #6
    Join Date
    Jun 2012
    Location
    northern CA
    Posts
    962
    Feedback Score
    2 (100%)
    Quote Originally Posted by Clint View Post
    The 12.5" MID configuration is best suited to a dedicated suppressed role.
    My plan is for a dedicated suppressed rifle, but I just want to see if it will run without a suppressor. If it won't run without a suppressor I will not open the port until it runs, I may open it slightly if it appears it may run with a minor adjustment.

  7. #7
    Join Date
    Dec 2015
    Posts
    539
    Feedback Score
    1 (100%)
    SOLGW is pretty transparent about their gas port sizes, and they do 0.078" for a 13.7 mid. They don't seem to believe in gassing guns for the bare minimum, instead preferring to design their guns to run when dirty, cold, etc. But still, I think a 0.075" 12.5" mid unsuppressed may be undergassed. According to a few sources, that's a smaller port than my 16" BCM mid (0.076").

    I don't claim to know much, but I read somewhere on here that there's more to it than simple port size. Barrel profile comes into play, as well as other things like port geometry and the taper of the bore. The short version was that (all else being equal) a pencil barrel will have more gas drive than a HBAR profile barrel with the same port size.

  8. #8
    Join Date
    Mar 2012
    Posts
    153
    Feedback Score
    6 (100%)
    I have a 12.5 mid from ar15 performance. No issues with or without suppressor and h2 buffer running 77gr mk262 clone.

    Sent from my SM-G973U using Tapatalk

  9. #9
    Join Date
    Sep 2007
    Posts
    3,748
    Feedback Score
    22 (100%)
    Quote Originally Posted by Clint View Post
    The 12.5" MID configuration is best suited to a dedicated suppressed role.
    This. For both suppressed and unsuppressed get a 12.5" carbine with a 0.069" port.

  10. #10
    Join Date
    Dec 2010
    Posts
    1,300
    Feedback Score
    7 (100%)
    Quote Originally Posted by 454308 View Post
    I have a 12.5 mid from ar15 performance. No issues with or without suppressor and h2 buffer running 77gr mk262 clone.

    Sent from my SM-G973U using Tapatalk
    IWI sells a 12.5 mid pistol Zion. If they are comfortable selling it to the general public, it must be reasonably reliable.


    Sent from my iPhone using Tapatalk

Page 1 of 4 123 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •