Quantcast

10.5" or 11.5" barrel for carbine gas system?

Discussion in 'NFA Firearms and Accessories' started by Ryanxia, Feb 5, 2018.

  1. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    I researched this quite a while back and don't remember what the general consensus was (if there was one).

    Is there an optimal barrel length between 10.5" or 11.5" barrel when using a carbine length gas system?

    I know either will shoot fine, and I'll be using an adjustable gas block I'm just curious if anyone knows if there is a noticeable different between recoil impulse / smoothness in shooting? I know pressures change a decent amount the further/closer the muzzle is from the gas port, I just don't remember which direction.

    Thanks for any input.
     
  2. Wisco

    Wisco Member

    Joined:
    Dec 13, 2013
    Messages:
    744
    I saw you just posted this. I was looking for something else, but I’ll stop and give you my two cents...

    I have a BCM 11.5. I’ve shot both a civilian DD MK18 and a Colt 10.3 or 10.5. And whatever the Army had a decade ago Colt Commando or maybe it was a MK18.

    From everything I’ve read, BCM and some Colts use the 11.5 because it’s optimal.

    I cannot tell the difference in shooting any of them between the 10.5 and 11.5. All have the same recoil and big blast. That was with a range of ammo. 55fmj to 77otm.

    I know is my 11.5 is 100% reliable. And my friends with other SBRs say the same about theirs - DD and Colt.

    Your adjustable gas block may solve any of problems associated with short carbine barrels.
     
  3. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    Thanks Wisco. I have a couple of 10.5" SBR's but I'm building another one to make my 'primary' rifle and just not sure if 11.5" would be better, I seem to recall that it was slightly better. Never had any issues with my other ones but might as well try to squeeze as much as I can out of it if I have the option when buying.
     
  4. Wisco

    Wisco Member

    Joined:
    Dec 13, 2013
    Messages:
    744
    No problem.

    There’s something about dwell time that I don’t quite fully understand that supposedly has to do with 11.5 being better, but maybe that’s negated by a larger gas port?

    I’m the opposite of you and looking at the 10.3 for my next upper because I feel like another inch is getting more of my money’s worth of the $200 tax stamp:)
     
  5. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    That's part of the reason I'm asking, I don't want to add an extra inch for no reason. :D

    But I have a 6.5" AR that I can play with if I want to go really short. :)
     
  6. MachIVshooter

    MachIVshooter Member

    Joined:
    Aug 11, 2005
    Messages:
    15,434
    Location:
    Elbert County, CO
    The difference is pretty negligible, although shorter dwell time is going to work better suppressed. Not that it matters if you're running an adjustable GB.
     
  7. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    Adjustable gas block aside, the shorter barrel is the shorter dwell time?
     
  8. Browning

    Browning Member

    Joined:
    Mar 21, 2007
    Messages:
    1,750
    Location:
    DFW - TX
    I've heard repeatedly that 11.5 inch is more reliable, but I was never sure if that was people just regurgitating internet lore or what.

    That being said I have a 10.5 inch and it's been pretty reliable (one stuck steel case after mixing brass and steel cased ammo in a really dirty gun out of perhaps 5k rds).
     
  9. MachIVshooter

    MachIVshooter Member

    Joined:
    Aug 11, 2005
    Messages:
    15,434
    Location:
    Elbert County, CO
    Yes, and my 10.5" runs well suppressed and unsuppressed with a standard GB
     
  10. Bwana John

    Bwana John Member

    Joined:
    Sep 10, 2004
    Messages:
    1,921
    Didn't the military use 11.5" because of minimum energy/velocity requirements, not because of any reliability concerns?
     
  11. Jackal

    Jackal Member

    Joined:
    Mar 9, 2006
    Messages:
    4,808
    Location:
    Northwest Washington
    I cant notice a difference in 10.5 or 11.5 carbine length OR 11.5 with mid length gas (Faxon Big Gunner). They all feel the same with adjustable gas blocks. The real difference is downrange. That extra inch gains you a pretty significant boost in ballistics.
     
  12. MachIVshooter

    MachIVshooter Member

    Joined:
    Aug 11, 2005
    Messages:
    15,434
    Location:
    Elbert County, CO
    Military uses the 14.5" M4 & M4A1, and then the 10.3" CQBR upper. The XM177 had both 10.5" and 11.5" barrels.
     
  13. JeeperCreeper

    JeeperCreeper Member

    Joined:
    Aug 23, 2014
    Messages:
    1,019
    Location:
    Under A Rock
    I have an 11.5 and it runs great. Not very scientific, I know....

    But if you're doing a pistol, the 11.5" puts it at the overall length to run a VFG... I think. I dont run one, but I think that's why I went with the extra inch. Sorry if that's a derail. And someone please correct me if I'm wrong.
     
  14. MachIVshooter

    MachIVshooter Member

    Joined:
    Aug 11, 2005
    Messages:
    15,434
    Location:
    Elbert County, CO
    You can make 26" OAL with an 8.5" barrel
     
  15. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    No pistols, I do SBR's. Thanks for all of the input. My main interest was in the smoothness but as some have stated it won't make a noticeable difference with an adjustable gas block. I'll just have to decide if I want the extra inch for the ballistics but probably I'll stick with another 10.5" since I will be running a suppressor on it as well and want to keep the length down.
     
  16. MistWolf

    MistWolf Member

    Joined:
    Aug 17, 2005
    Messages:
    2,679
    I've used both the 10.5" and 11.5" barrel fitted with an adjustable gas block, with and without suppressors. The main difference I've noticed between the two is drop and energy at three hundred yards. The 11.5" barrel has a noticeable edge.

    The biggest difference in smoothness and soft recoil came with choosing a buffer and recoil spring. I tried the carbine, H and H2 buffers with a standard carbine spring. The H2 buffer felt the softest of the three.

    What felt even softer was the A5 RE, A5H2 buffer and the Sprinco green action spring.

    My favorite combination is the 11.5" barrel, SLR adjustable gas block and A5 RE assembly with a suppressor.
     
  17. WestKentucky

    WestKentucky Member

    Joined:
    Feb 1, 2014
    Messages:
    6,247
    Location:
    Middle Tn
    Carbine gas tube is 7.5 inches long. You need barrel length from that gas port forward to hold pressure on the system to operate the action. Either length should be fine, especially if a suppressor is used. Just gotta make sure you have pressure high enough and for long enough to cycle the action.
     
  18. FL-NC

    FL-NC Member

    Joined:
    Feb 10, 2016
    Messages:
    3,079
    Location:
    Fl panhandle
    I prefer a 11.5" with heavy profile. We had 10.5" at work, and I used a 11.5" on one deployment. I think the extra length and weight up front is an advantage when firing fast.
     
    Ryanxia likes this.
  19. Sebastian the Ibis
    • Contributing Member

    Sebastian the Ibis Member

    Joined:
    Mar 30, 2008
    Messages:
    1,916
    Location:
    "The Gunshine State"
    I have and like my 10.5.

    If you don't mind used and waiting,
    Summitgunbroker has nicely built out 11.5 trade ins for far less than the components (surefire light, aimpoint) would cost.
     
    Ryanxia likes this.
  20. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    That's some really good input. Thanks a lot for sharing. And thanks to everyone else as well.
     
  21. Ryanxia

    Ryanxia Member

    Joined:
    Jun 18, 2010
    Messages:
    4,506
    Location:
    'MURICA!
    I'm also thinking of doing some more research on the adjustable bolt carrier groups that are out. Gemtech makes one with a suppressed and unsuppressed setting and Bootleg makes one with 4 positions although it lacks notches for forward assist.
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice