Difference between an AR-15 or M4 carbine

Discussion in 'AR-15 Discussion' started by ccase39, Apr 30, 2013.

  1. ccase39

    ccase39 New Member

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    am having a difficult time understanding the difference between the two. Also the M-10. As I understand it the AR-10 came first from Amaralite and the AR-15 came based off that. Is the M-4 just the military version? Little history lesson here please.
     
  2. AgentTikki

    AgentTikki New Member

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    M4 is an automatic or select fire version of the AR15 with a 14.5" barrel.
     

  3. clr8ter

    clr8ter New Member

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    But, they put some of the M4 upgrades in semi-autos, and sell them to us regular people as M4's, no? Sometimes called M4geries?
     
  4. SSGN_Doc

    SSGN_Doc Well-Known Member

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    The M4 specific features, besides select fire, that should be on a AR model being sold as an M4 type should include:

    Grenade launcher mounting cuts in the barrel.
    1:7 rifling twist.
    Chrome lined bore and chamber
    Enlarged feed ramps
    Flat top upper with feed ramp extension cuts
    6 position collapsible stock with mil spec diameter receiver extension
    Bolt carrier with shrouded firing pin
    Gas key that is staked
    Extractor with carbine extractor spring and buffer and o ring.

    Some M4geries will just have the grenade launcher cuts, whatever collapsible stock and commercial receiver extension, a flat top and they'll call it good enough to be a visual representation of an m4.
     
  5. SSGSF

    SSGSF New Member

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    The m4 has a 16in barrel not a 14.5. And the ar15 has a 20 in barrel .
     
  6. JonM

    JonM Moderator

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    The civvy version is 16" military 14.5". Ar15 can be anywhere from 9-26" depending on taxes and paperwork and who is making it.

    What we call m4 are just ar15 dressed up to resemble the military carbine.

    The common ar15 is not much different than grandpappy's m1 garand from ww2 or uncle jimbob's remington autoloading deer getter. It fires one bullet each time the trigger is pulled.
     
  7. Quentin

    Quentin New Member

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    The AR-15 was the 15th firearm designed by ArmaLite back in the 1950s. Colt bought the rights to the rifle and by 1963 our military began buying them in quantity and eventually it became the M16. Civilian (semiauto) versions continued to be sold as the AR-15. At first the barrel length normally was 20" but carbines soon showed up. Today the military has moved toward the 14.5" M4 and civilians often buy the 16" semiauto version of the M4, for example the Colt 6920.

    Anyway, AR-15 now is a generic term for a family of rifles/carbines/pistols and M4/M4gery is one of the carbine versions. Of course there are many, many brands besides Colt today and hundreds of different names for their products. We tend to lump them together as the AR-15 since they are largely compatible with the rifle of the 1960s.
     
  8. clr8ter

    clr8ter New Member

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    Correct me if I'm wrong, but the Colt LE6920 meets this list? Minus the 14.5" barrel, of course......
     
  9. Quentin

    Quentin New Member

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    Yes the Colt LE6920 meets that list. It's a semiauto 16" version of Colt's military M4.

    The last line about the extractor... I've heard it called black insert not buffer and the O-ring may or may not be installed.
     
    Last edited: May 1, 2013
  10. SSGN_Doc

    SSGN_Doc Well-Known Member

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    Correct. I've heard the urethane plug refered to as an insert or a buffer, and I've seen themn in blue or black. And you are also correct that some will not have the o-ring, and some may or may not have a D shaped ring instead. Thanks for adding the clarification.

    Since they are under the extractor, it's usually not something you are going to get to check out in a gun store before you buy.
     
  11. Quentin

    Quentin New Member

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    I've heard the insert must be black in military M4s. Blue is acceptable in the M16 but they're being replaced as a wear item with the black insert and corresponding spring. O-rings are preferred in the M4 but many of us remove them from our semiauto versions.
     
  12. clr8ter

    clr8ter New Member

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    So what is the function of this popularly-debated o ring/buffer/whatever it is? Why does the military care what color an unseen part is?
     
  13. JonM

    JonM Moderator

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    It aids in extraction in overgassed guns (most carbine length gas systems) and with the m4 14.5" barreled gas system.

    What happens is the gas system in a carbine length is so short and often oversized in longer barrels the case hasnt had enough time to shrink after firing before the gun starts extracting. The black oring is a brute force solution to design problem with short gas tubes and short barrels.

    Midlength gas systems solve this issue in 16" barrels hence their populaity
     
  14. SSGN_Doc

    SSGN_Doc Well-Known Member

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    The color of the unseen part is to color code it for how firm it is. Blue is for rifles, Black is for carbines. I've seen both in both.
     
  15. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    A Colt model LE6921 is the closest thing an individual can, since 1986, legally purchase to a US military M4 carbine. The only difference between the LE6921 and the M4 carbine are the fire control parts and the lack of a sear pin hole in the receiver.

    The extractor "o-ring" is an inexpensive solution to a problem that should have been resolved with higher quality extractor springs. The military is always looking for new and inventive ways to save a buck or two, which is the reason behind the blue and black o-rings.

    The 16" barrels with carbine length gas systems have two things going against them:

    1. Dwell time - After extensive testing the military determined that having 4 inches of barrel in front of the gas port was about optimal. The M16 rifles and M4 carbines have that magic 4 inches of barrel in front of their gas ports. The 16" barreled carbines with carbine length gas systems have an extra 1.5", roughly, in front of the gas port. The "mid-length" AR's locate the gas port further forward to make up the difference.

    2. Location of the gas port - It shouldn't be a big surprise that the closer the gas port is to the chamber, the higher the pressure in the barrel will be.

    As JonM noted, most AR's to include military AR's, use more gas than necessary to forcefully operate the action of the rifle or carbine. The result is greater wear and tear on the operating components and shortened service lives. Automatic, burst and fully automatic, modes of operation cause problems not generally experienced by civilian AR users (like extraction failures, bolt bounce, overriding cartridges from magazines with weak springs, and a number of other not-so-great side-effects).

    Unless you're a government user you probably won't have to worry about the auto problems, but you may have extraction problems from worn, damaged, or out-of-spec components. The best answer to the extraction problem is a better spring, not rubber or plastic doo-dads.
     
  16. clr8ter

    clr8ter New Member

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    Verrrry interesting. Now I'm curious as to what color is in mine. But regarding the spring KBD512, is the spring you speak of available as a fix for the problem?
     
  17. Quentin

    Quentin New Member

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    I'm not KBD but BCM sells an extractor upgrade kit with the proper spring and black insert. I have three on hand since they are small and cheap. Good idea to order a few spares.
     
  18. clr8ter

    clr8ter New Member

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    Cool, thanks.
     
  19. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    clr8ter,

    I'm speaking of chrome silicon extractor springs from manufacturers like David Tubb (davidtubb.com) and Sprinco (sprinco.com). I'm sure there are others, but those two immediately jump to mind and are things that I use.

    The materials that most manufacturers use and many military specifications denote are about cost/economy, not about the best performing components for the job.

    With a proper chrome silicon extractor spring you don't need little rubber parts to make your extractor grip the case rim with enough force to assure a reliable extraction. In fact, Tubb tells you not to use a D ring with his extractor springs. I'm not sure about Sprinco, but I'd bet that they'd tell you the same thing.

    The point is, better materials technology and better manufacturing methods produce springs that function better and longer without replacement. The same is true of the buffer spring.

    With the number of compressions and level of heat your valve springs are subjected to, ever wonder why your car can go so many tens of thousands of miles before those components wear to the point that they have to be replaced? Ever wonder why, if that's possible in an internal combustion engine, it would be necessary to replace a buffer spring or extractor spring after a few thousand rounds?
     
  20. clr8ter

    clr8ter New Member

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    Oh, no, i'm aware of that, I don't wonder. I am new to Ar's, though, so I'm not fully up on what all the parts do, and if there are better replacements out there. Thanks for the info.