WHY HAVE DIFFERENT LENGTHS? ie. carbine, mid, rifle.

Discussion in 'AR-15 Discussion' started by Broke124, Nov 28, 2011.

  1. Broke124

    Broke124 New Member

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    What are the main reasons for different length AR's? What are advantages/disadvantages of each?

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  2. JonM

    JonM Moderator

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    carbine length is actually designed for a 14.5 inch m4 military barrel not the 16 inch civvy carbines. midlength works MUCH better on a 16" barrel much better smoother recoil impulse. rifle length is even smoother than mid. thats why the first m16 barrels were 20". the shorter you go the more difficult it becomes to maintain a AR15. you get more parts breakage due to the increased forces of the shorter carbine tube.

    i just dont see the point of a carbine length tube on a 16" barrel. it doesnt make sense to me.
     

  3. Broke124

    Broke124 New Member

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    So I'd want a rifle length on a 16" barrel ideally?

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  4. Quentin

    Quentin New Member

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    Broke, did you read what JonM said? Though none of us know what you want he clearly stated what most people consider the best gas length for the 16" barrel. Clue: he didn't say rifle length or carbine length.
     
  5. Broke124

    Broke124 New Member

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    Then he said rifle is even better. So now I'm confused.

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  6. JonM

    JonM Moderator

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    rifle length on a 16" doesnt allow enough room at the end to give the gas time to work the action you end up with short stroking problems. mid length is the longest that works reliably. you MIGHT get away with a rifle length running with little trouble if you use a suppressor 100% of the time.

    on a 16" midlength is ideal. the reason you dont see it offered a lot is because of the popularity of the carbine look and most of the aftermarket rail systems are carbine length. midlength is becoming more popular.

    if your going 20" then full rifle length. its all got to do with gas pressure. the closer the gas port is to the chamber the higher the pressure is delivering more force to the gaskey on the bolt body. for carbines to work right you have to make the gas port smaller to reduce the ammount of gas. with a smaller gas port you run into reliability issues with the port getting clogged and under powered ammo not having enough ooomph.

    mid length gives you the ability to operate at a larger gas opening smoothing out the impulse and rifle does an even better job. when you see people having problems with cheap ammo its always carbine gas systems. rifle and mids are more reliable.

    anyway those arent hard fast rules just kinda guildlines. there are carbines that will run thousands of rounds no issues on the cheapest ammo out there. there are rifle length that will have problems with prmium ammo. its just a general idea of the theories behind and why there are different lengths.

    i personally dont see a purpose in the civvy non-nfa non-ar pistol world for carbine gas tubes
     
  7. mjkeat

    mjkeat New Member

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    This question seems to have come up at least a couple times here recently.
     
  8. Jpyle

    Jpyle New Member

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    In a world where engineers make the rules function would always win out over form but I suspect that the aestheticly appealing carbine length handguards drive much of the popularity of the carbine length gas systems. Opposite applies to the "old school" look of the rifle length systems. JMHO...
     
  9. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

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    I would disagree that the carbine length was developed for the 14.5" barrel as the 16" carbine pre-dates the 14.5" by about 30 years.

    I do not see a problem with a 16" carbine length set up. I have run many thousands of rounds through mine w/o any breakage. I run a "H" buffer and enhanced extractor spring.
     
  10. Broke124

    Broke124 New Member

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    What does H buffer mean?

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  11. dmp

    dmp New Member

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    Broke - if you go to your profile, you can add that bottom line as your signature; to keep from having to re-type it. :)
     
  12. Broke124

    Broke124 New Member

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    It is my signature. I promise I wouldn't re-type all that everytime. Lol

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  13. Broke124

    Broke124 New Member

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    Yeah I could never get the direct, to the point answer I was needing until now. :/ so that would be my fault.

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  14. JonM

    JonM Moderator

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    "H"Buffer is a heavier buffer for carbines to help with the increased gas pressure. Its marked H so you know the diff.
     
  15. Broke124

    Broke124 New Member

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    Would an H buffer work better in a mid-length?

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  16. Quentin

    Quentin New Member

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    It depends. On the gas port size, BCG mass, strength of the ammo you'll use, lots of things. Many people use the regular carbine weight buffer but an H usually works. I have an even heavier (+0.9 oz.) H2 in my ArmaLite middy since its BCG is the AR-15 style which is about 1/2-3/4 oz lighter) than M16 weight. I have the H in my Daniel Defense middy because it has the heavier DD BCG. The BCG + buffer weight is about the same in both rifles and low powered ammo cycles the action just fine. The H2 + DD BCG might not cycle but I've never bothered to try it.

    You have to give it some thought then go with it. Too much weight then you might need a lighter buffer but they're not that expensive.
     
  17. Broke124

    Broke124 New Member

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    Well I'm going to be getting a v5 DD mid length upper so if the H buffer might work better then that's prob what I'll go with. I'm assuming BCG means "bolt carrier group" ?

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  18. mjkeat

    mjkeat New Member

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    Correct on the meaning of BCG.

    I use an A5 VLTOR buffer system on my DD now which replaced a standard mil-spec extension w/ a Spikes T2 buffer. Both worked great

    Try different things and see what works for you. The H is a great place to start.
     
  19. Broke124

    Broke124 New Member

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    What differences can I expect between the different buffers? Are the differences mainly recoil related or what?. BTW I'll be running it on a V5 LW if that makes a difference. Don't know if the LW affects anything with that.

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\
     
  20. Broke124

    Broke124 New Member

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    So do you get an extension just to make the stock longer or are there other reasons?

    "...rough men stand ready in the night to visit violence on those who would do us harm." /G\