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Thread: Carbine vs Mid

  1. #31
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    dwell increase

    no, people are doing it now, just not advertising it,

    this is done on the shrike AR style system, it doesn't change much of anything in the end. you can see it more upclose under the industry section in ARfcom.

    On that system notice the stepped pin, that is because of the huge dwell addition. You can split the difference and not have to do that.

    Not a different system at all, just a small tweak

    **Did you know(this could be wrong) that in the beginning(stoner days), they didn't put a dwell in carrier, immediately noticed an issue and a dwell was added, it certainly wasn't tweaked when they shitcanned it to make the M4.

  2. #32
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    I have a few questions.

    The fellow over at 03designgroup has mentioned he has cut his carbine gas system rifles down to 14.5 and his middys at 16 so they have the same length of barrel forward of the gas port. Is this the key to the middy vs. carbine debate?

    Also vuurwapen blog mentioned how Colt's 16 carbine gas system guns had bigger gas holes in the barrels than their 14.5 counterparts. Is this something we need to account for, gas hole size?

    I remember Ken Elmore before he left Colt in my AR-15 armorer's course discussing the gas system at the end of class. He wrote up on the board some thing like this:

    __________A_____________/\_______B___

    A being the part of the barrel before the gas hole.
    /\ being the gas hole.
    B being the part of the barrel forward of the gas hole.

    Ken said if you change one of those you have to change the others otherwise you are going to have problems. It was part of his warning to us not to cut barrels down without having someone do it who really understood how changing one changed the others. He was really talking about changing B. He pointed out that the Commando, M4, and M16 gas ports went big, small, and big. Commando was big because it needed gas now, M4 small because it had time with a longer B, and M16 big again because it needed more gas for the long A.

    The question I have besides the one above is how does changing A 2 inches forward in a 16 inch gun affect /\. Does /\ need to be bigger or smaller? What about taking a 16 carbine and cutting 1.5 inches off of B?
    Last edited by cacop; 11-11-10 at 22:04.

  3. #33
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    Quote Originally Posted by kal View Post
    what you're promoting would require the action to be longer, thus, creating a proprietary rifle that would be longer than the ar15 and have proprietary internals. That's unacceptable.

    It's easier to move the gas port closer to the muzzle.
    No he isn't.

    He is talking about using the cam path on the LMT Enhanced carrier on a carrier with standard gas venting.

    Such a carrier would be useable in any length configuration and only make them all run better IMO.
    My brother saw Deliverance and bought a Bow. I saw Deliverance and bought an AR-15.

  4. #34
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    Quote Originally Posted by markm View Post
    I have a POS Bushmaster 14.5" carbean upper with like 30k rounds through it. It still head spaces ok, and will hold under 2" groups at 100 as of last weekend.

    If you're shooting only 1000 per year... you'll get at least 30 years useage out of it.... give or take.
    Is everything original on the gun? That is impressive.
    "Real men have always needed to know what time it is so they are at the airfield on time, pumping rounds into savages at the right time, etc. Being able to see such in the dark while light weights were comfy in bed without using a light required luminous material." -Originally Posted by ramairthree

  5. #35
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    Quote Originally Posted by cacop View Post
    I have a few questions.

    The fellow over at 03designgroup has mentioned he has cut his carbine gas system rifles down to 14.5 and his middys at 16 so they have the same length of barrel forward of the gas port. Is this the key to the middy vs. carbine debate?

    Also vuurwapen blog mentioned how Colt's 16 carbine gas system guns had bigger gas holes in the barrels than their 14.5 counterparts. Is this something we need to account for, gas hole size?

    I remember Ken Elmore before he left Colt in my AR-15 armorer's course discussing the gas system at the end of class. He wrote up on the board some thing like this:

    __________A_____________/\_______B___

    A being the part of the barrel before the gas hole.
    /\ being the gas hole.
    B being the part of the barrel forward of the gas hole.

    Ken said if you change one of those you have to change the others otherwise you are going to have problems. It was part of his warning to us not to cut barrels down without having someone do it who really understood how changing one changed the others. He was really talking about changing B. He pointed out that the Commando, M4, and M16 gas ports went big, small, and big. Commando was big because it needed gas now, M4 small because it had time with a longer B, and M16 big again because it needed more gas for the long A.

    The question I have besides the one above is how does changing A 2 inches forward in a 16 inch gun affect /\. Does /\ need to be bigger or smaller? What about taking a 16 carbine and cutting 1.5 inches off of B?
    it's not about set lengths, its about ratio. the gas port should be about 5/8ths of the way down the barrel from the bolt face.. .625% gas to .375 dwell, or something close to that.

    gas port size is more complicated.. but as you said, short dwell- larger port.. over-dwelled, shorter port.. longer system, larger port.

    unless you're sabre.. then you just use .080 for everything.
    Last edited by bkb0000; 11-11-10 at 23:37.

  6. #36
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    Quote Originally Posted by glockkid88 View Post
    This thread is a big relief to me. I just purchased a ddm4 carbine about 2 months ago. I was sure that I had bought the best carbine in my price range until I started seeing the craze for midlength systems. I found thinking that I may have made the wrong decision and maybe should have bought a midlength carbine. I am new to the rifles and am trying not to get too caught up in the newest coolest shit craze. I almost bought a new lower to build a midlenght m4 recently but now I think that the money would be better spent on ammo and learning to shoot the carbine length system I have. I will probably shoot no more than 5k next year and I am sure the ddm4 will serve me well.
    Best statement in this thread.

  7. #37
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    Dwell

    Quote Originally Posted by Heavy Metal View Post
    No he isn't.

    He is talking about using the cam path on the LMT Enhanced carrier on a carrier with standard gas venting.

    Such a carrier would be useable in any length configuration and only make them all run better IMO.
    This is correct, I was unaware that it was public knowledge for LMT with their carrier. More Dwell is in no way harmful, at all. It makes up for many situations gone bad because of unlock timing and pressures. I wish this was pushed more as a solution that should be implemented on all AR brands, it is only a change in the 4-AXIS CNC program cutting the slot, the gas port location is still very critical but this would really really help extraction and hence reliability.

  8. #38
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    Quote Originally Posted by armatac View Post
    This is correct, I was unaware that it was public knowledge for LMT with their carrier. More Dwell is in no way harmful, at all. It makes up for many situations gone bad because of unlock timing and pressures. I wish this was pushed more as a solution that should be implemented on all AR brands, it is only a change in the 4-AXIS CNC program cutting the slot, the gas port location is still very critical but this would really really help extraction and hence reliability.
    Smart guys here

  9. #39
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    The philosophy I subscribe to is run the longest gas system you can in DI.

    If that's Midlength because you have a 14.5''+ barrel, if that's a Rifle Length at 18''+, Carbine length at 14.5''or less. (And honestly, alot of people are having great results with running Mid-Length gas systems on 14.5'' so I might just run a carbine length on barrel lengths shorter than 14.5'')

    I mean, faster gas port erosion, faster parts wear at higher pressures and more are the concerns.

    But again, I haven't seen those documented. They would seem to be true, but I haven't seen it tested either.

    What you do know is that it gives more dwell time and less recoil for 2'' of gas tube, a longer handguard, (which IMHO is better for handling the weapon, and even if you don't handle way out there, it's nice to have options, you can attach a bipod, etc.), and usually has a lot less extractor issues as it isn't as "violent" extraction.

    Use what you want, but I don't see a downside with going with the longest gas system available as a general rule of thumb.
    Last edited by BWT; 11-12-10 at 15:23.

  10. #40
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    The only 5.56 bolts I have broken were in carbine gas rifles, one was a Y/M chrome bolt that may have only lasted 1000 rounds the others lasted 4-5000 and they all broke at the cam pin hole. The DOD contractor produced bolts last much longer than the commercial grade bolts. After checking the hardness I do not believe the commercial bolts were Carpenter alloy #158(P6) or were hardened to mil spec. the bolts tested in the low 50s.
    Off on a small tangent it appears most chrome carriers are deco chrome(like a car bumper) not hard chrome like the bore inside of a mil spec carrier.

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