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Cut the barrel on a 6920?

Discussion in 'Black Rifle Forum' started by samuse, Jan 25, 2011.

  1. samuse

    samuse

    5,375
    21
    Jul 30, 2008
    South TX
    I keep hearing that the 16" bbl is really not optimal for the carbine length gas system.

    Would cutting the barrel down to 14 1/2" and pinning the flash hider be a better setup than the 16"?

    Or not matter?
     
  2. RMTactical

    RMTactical www.AR15pro.net CLM

    12,603
    16
    Oct 7, 2000
    Behind an AR-15
    If you feel like you are up to the job...

    I prefer my 16" AR's to be midlengths and the 14.5" AR's to be carbine length. I find that I just prefer the 14.5" w/ a permanently attached flash hider above anything else...

    [​IMG]
     


  3. jdodd

    jdodd

    434
    0
    Dec 21, 2009
    It just comes down to personal preference. You are not losing anything real world with a 16" carbine.

    My go to shop is ADCO, they have a quick turn around and do top quality work. I just had them re-work my newest AR and I couldn't be more pleased. Ill have to post up pictures sometime today.

    http://adcofirearms.com/shopservices/

    I can provide other shop names...but thats who I would go to.

    -J
     
    Last edited: Jan 25, 2011
  4. RMTactical

    RMTactical www.AR15pro.net CLM

    12,603
    16
    Oct 7, 2000
    Behind an AR-15
    I did one and BCM did the other. They were 14.5" barrel from the factory though. I didn't cut it down (I pinned and welded the flash hider though), although my brother and I did one like that with a superlight barrel once.
     
    Last edited: Jan 25, 2011
  5. K. Foster

    K. Foster

    2,462
    367
    Feb 19, 2002
    Mo.
    Cutting your barrel just to optimize your gas system is not a good idea. If you want an optimized gas system with either a 14 ½ or 16" barrel, you should get a mid length upper. A mid length does provide a slightly softer recoil impulse but the difference is minor. If you were buying a new upper...yes, get a middy. But I recommend leaving the Colt as is.
     
  6. thisaway

    thisaway Moderator

    1,580
    3
    Jan 11, 2000
    Soddy Daisy, Tenn.
    I do not recommend that you cut the barrel on your Colt upper. Try buying a BCM 14.5-inch mid-gas-length upper to better match your performance requirements, and keep the Colt as a spare.
     
  7. glock22357

    glock22357 Got Ammo???

    3,163
    0
    Mar 1, 2004
    Benton Harbor, MI
    OP; Why do you think it's necessary to cut the barrel on your 6920? What do you think you will gain in doing that?
     
  8. samuse

    samuse

    5,375
    21
    Jul 30, 2008
    South TX

    I didn't think that it was necessary, I was just wondering if a 14.5" barrel is a better match for the carbine length gas system.
     
  9. RMTactical

    RMTactical www.AR15pro.net CLM

    12,603
    16
    Oct 7, 2000
    Behind an AR-15
    The short answer is yes.
     
  10. mvician

    mvician Lifetime Member

    3,149
    7
    Jun 8, 2007
    NW Indiana
    16" barrels with carbine gas systems has worked for years. Leave your 6920 alone.
     
  11. glock22357

    glock22357 Got Ammo???

    3,163
    0
    Mar 1, 2004
    Benton Harbor, MI

    Let's be clear about what the OP is really asking about. This isn't a question on aesthetics or preference.

    The OP has gotten some bad info from somewhere, and has been lead to believe that there is a mechanical ratio or "match" between barrel length and gas system length, to the point where he believes he needs to chop his barrel to "match" his gas system.

    No, cutting the barrel on your 6920 down will not make any difference in the operation of your rifle, other than losing you some velocity. It's not like there is some mechanical "match" relationship between barrel lenth and gas system, it's just which length gas system you have on your AR. The length of the barrel is not the issue, it's just that the shorter length gas system is slightly harsher on the operation of the rifle. Unless you shoot tens of thousands of rounds a month, and want your AR to last five life times, there's no practical difference in gas system lengths.

    The only way to make an actual change is to get a new barrel, mid-(or rifle) length gas system, spring, buffer, hand guards, and front sight/gas block installed. This is just shy of pointless, a bit expensive, and won't reap the OP any practical benefits. The OP would be far better off just getting an entire mid-length gas system upper, and even then the difference would hardly be noticeable.
     
    Last edited: Jan 28, 2011
  12. samuse

    samuse

    5,375
    21
    Jul 30, 2008
    South TX
    So I think the answer is clear. Since there is no real good reason to cut my barrel, I'm gonna leave the 6920 totally unmolested and buy a BCM A4 rifle.

    That's what ya'll said right?:)
     
  13. glock22357

    glock22357 Got Ammo???

    3,163
    0
    Mar 1, 2004
    Benton Harbor, MI
    Lotsa answers.........all over the board, right?:rofl::rofl:

    Yeah, just either get a new BCM upper (a good, cost effective answer) and put it on your Colt's lower, or get another rifle.

    One cool thing is that getting an upper is just a question of ordering and having shipped to your home. If you get an entire rifle, ya gotta do your forms and such.

    Is an M16A4 what you're looking to get?
     
    Last edited: Jan 28, 2011
  14. surf

    surf

    1,019
    4
    Jul 7, 2010
    Just to clarify, the Colt CAR length gas system on a 14.5" barrel will have the same gas port size as does the 16" version. The 2 will run slightly different however since both will work well it might be a moot point of which actually works better. So in essence one may be more "optimal" than the other however since both work well no one really notices, but there is a technical difference in a few aspects. Also with non milspec rifle types, you may have variances when talking barrel lengths in relation to gas port sizing so there is no real "standard" to go by.

    This statement however is not true. Just to clarify so that someone does not think that they can cut their CAR length barrel from 16.1" to 10" and be OK, well they will not be OK. SBR legal considerations in mind, the barrel length will directly affect how the weapon functions. Or more importantly the relationship of the length of the barrel after the gas port and the actual diameter of the gas port itself. So there is a "match" relationship in barrel length and gas system. Do it yourself and you had best understand gas port sizing and perhaps altering other aspects of the rifles systems. However when you purchase off the rack, it has usually been done by the manufacturer. However you may still need to alter or change some components to optimize your rifles performance or to ensure that it runs period.

    So yes there is a technical difference in what may be "optimal" in your original question, however from a user standpoint, you will not notice a difference. I do however prefer a shorter barrel in a carbine, even if it is only 1.5". Of course shorter is better for most of my carbine needs and 10"-12" is my preferred barrel length on a carbine.
     
    Last edited: Jan 28, 2011
  15. 12131

    12131 Monkeyboy CLM

    6,280
    6
    Nov 17, 2006
    God's Country (Texas)
    Exactly!
    If you have shot your 6920, and it's fine (and I suspect it is, just like millions of 16 in. ARs out there, already), stop messing up your fine rifle, based on what you read on the internet.
     
  16. RMTactical

    RMTactical www.AR15pro.net CLM

    12,603
    16
    Oct 7, 2000
    Behind an AR-15
    You don't need to cut the barrel. No. However the 14.5" barrel on a carbine gas system is a better fit than the 16".

    Its not a big deal. I prefer the 14.5" for other reasons.

    However I wouldn't cut a 6920. Id just sell it and get a 14.5"
     
  17. Alaskapopo

    Alaskapopo NRA ENDOWMENT

    6,545
    2
    Feb 6, 2000
    Alaska
    I would not. I have a 14.5 inch Noveske with a perm muzzle brake and while it is a good shooter I am stuck with that muzzle device and I have wanted to switch it out. But doing so would ruin the current expensive brake and if done wrong could hurt the barrel as well. I would get a 16 inch mid length instead.
    Carbine gas system is not as good. It kicks more and has a shorter service life.
    Pat
     
  18. glock22357

    glock22357 Got Ammo???

    3,163
    0
    Mar 1, 2004
    Benton Harbor, MI
    You're writting is not very clear on what point you are trying to convey in an effort to actually answer the OP's question. You are discussing 2 variables, gas port size and barrel length, when that has not been the discussion at hand. What has been discussed (up to your post) is the relationship between barrel length and gas system length (i.e. carbine vrs. mid vrs. rifle length.) Then, you further muddy the waters of what is being discussed by bring SBRs into the picture, in an apparent attempt to rationalize discussing gas port size.

    O.K., we'll hang in there with ya.......but.....

    You're stating as fact that there is a difference in the operation of otherwise identical 6920s, one having a 14.5" barrel and one having a 16" barrel, due to the 1.5" difference in barrel length after the gas port.

    Please provide some emperical evidence to support this claim.
     
    Last edited: Jan 30, 2011
  19. I don't see anything wrong with chopping your Colt barrel if that's what you want and you don't mind losing some of the barrel markings and resale value. I would use ADCO for this type of work.

    ETA: if you do go for it, I would consider chopping the barrel to 14.7" and permanently attaching a standard A2 suppressor, rather than going 14.5" with an extended A2X. Both options will bring the overall length to 16". Just a thought.
     
    Last edited: Jan 30, 2011