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What's the difference between M16 and AR-15 (mechanically & legal)

Discussion in 'Firearms' started by Blackjack, Apr 18, 2007.

  1. Blackjack

    Blackjack Monkey+++

    I'm wondering what the difference is mechanically and legally between AR15's and M16's.

    My issued M16A1 obviously had a 3-position safety, but what else makes the difference? Is the upper completely the same?
  2. TnAndy

    TnAndy Senior Member Founding Member

    Re: What's the diff between M16 and AR15 (mechanically & leg

    Mechanically: the upper is the same.....the lower has an auto sear in it that allows the selector switch to hold the sear down for full auto....at least in the old "full rock and roll" models......I haven't got a clue how they did the 3rd burst thing. I have an AR-15 from the mid 70's, and have studied the sear.....it wouldn't be TOO hard to modify.....I think they changed that later.....I really haven't looked.

    That brings us to the 2nd part....Legally:

    Legally, you have to have a Class 3 permit and the full auto weapon has to be registered and the 200 buck stamp issued for it. I have no class 3, nor do I have any full auto......waste of money to me......govt is about the only one that can afford the feed and upkeep of them.

    I'll take well placed, single shots just about every time over "spray and pray".
  3. ex3313

    ex3313 Monkey+++

    Re: What's the diff between M16 and AR15 (mechanically & leg

    The bolt carrier is different between the two models the M16 has a small opening on the bottom to work with the auto sear.
    I just read the Bushmaster catalog and they say that any AR15 with M16 parts are considered to be full auto so check your guns.
  4. sniper-66

    sniper-66 Monkey+++ Moderator Emeritus Founding Member

    Re: What's the diff between M16 and AR15 (mechanically & leg

    All this talk about auto sears, I decided to take a look. I have my M4 sitting here, so I picked it up, broke it open and took a look-see. It has the three shot burst selector, so I thought I would try to figure out the sear. What I learned is that when you pull the trigger and hold it back and then push the hammer back to engage the burst sear, the hammer will lock down and not come back up, no matter what you do to the trigger. The only way to break the lock is to turn the selector to semi.
    I can see that I am going to have to investigate this one further.
  5. Paradoc

    Paradoc Retired Combat Medic

    Re: What's the diff between M16 and AR15 (mechanically & leg

    The differences are :

    Mechanically the lower receiver has an extra hole machined to pin the auto sear in place above the selector switch (also some manufacturer omit the machining inside the lower receiver to allow installation of an auto sear).

    The selector switch in the M16 has extra grooves to allow it to disable the disconnector.

    The disconnector has a little piece on the end of it that gets held down by the selector switch when placed in the auto/burst position.

    The trigger has an open back design to allow for the auto disconnector.

    The hammer has a hook to catch on the auto sear.

    The bolt carrier has a longer section on the lower rear portion to trip the auto sear and release the hammer as it slams forward to chamber the round allowing it to continue firing until you release the trigger, on burst models the disconnector is released by the burst cam after 3 shots and stops firing until the trigger is pulled again.

    Full auto and burst fire control groups both contain different parts from each other and the Semi Auto FCG.

    M16 bolt carriers are legal in AR15s (despite the Bushmaster website data) as they alone do not allow automatic operation, new Colt AR's come with the M16 bolt carrier installed from the factory and M16 carriers are available from many sources for around $130.00

    However, the fire control group (trigger, hammer, disconnector, selector, and auto sear) will get you federal prison time if you do not have a Tax Stamp to possess a full auto weapon (made prior to the 1986 Machine gun ban).
  6. Blackjack

    Blackjack Monkey+++

    Re: What's the diff between M16 and AR15 (mechanically & leg

    Good info.... thanks.
  7. Seacowboys

    Seacowboys Senior Member Founding Member

    Re: What's the diff between M16 and AR15 (mechanically & leg

    about $100.00 worth of fire-control parts from Bushmaster, an 1/8" drill, a dremel tool, and ...oh yea...maybe ten years in club fed.
  8. Tango3

    Tango3 Aimless wanderer

    Re: What's the diff between M16 and AR15 (mechanically & leg

    You don't need it.
    its illegal to screw around with it... get outta there while you still have your freedom.( first time somebody offers to sell you conversion parts, you'l end upo talking to a stern looking feddy wanting you to describe the contents of your friends gunsafes...).

    I don'tunderstand the fascination with full auto.Unless you want to do an "A team" and scare the bad guys off with noise.
    IMHO: If you are walking along and hear auto fire you are generally safe, its when you hear individual; semi auto AIMED SHOTS COMING YOURWAYare you in individual danger.
  9. Blackjack

    Blackjack Monkey+++

    Re: What's the diff between M16 and AR15 (mechanically & leg

    Nah, I don't want it.... too much hassle, I was just curious what the difference was. My old Colt M16A1 when I was in the army was an awful lot of fun though.

    If the feds started allowing it again without all the hoops to jump through, I'd want another one.
  10. Tango3

    Tango3 Aimless wanderer

    Re: What's the diff between M16 and AR15 (mechanically & leg

    And the chances of any of us buying even airsoft guns in the near future are getting slimmer by the day....Sorry for the smartass troll like response..didn't add any real information.[troll][troll][beat][beat][beat]NO!![touchdown][touchdown]
  11. Minuteman

    Minuteman Chaplain Moderator Founding Member

    Re: What's the diff between M16 and AR15 (mechanically & leg

    I have to agree with you Tango. I have never understood the appeal of full auto either. Other than the fun factor. The price and waste of ammo just doesn't seem to me to be worth it.
    What was it? An average of 50,000 rounds to one kill in Vietnam?While snipers averaged 1.5. There is a reason that the military has gone to 3 round burst.
    Spray and pray guns might be a gas to shoot but I don't see any tactical advantage other than a rare close quarters, house cleaning type of role.
    A marksman who can hit his target, especially at ranges that keep the enemy away from you, is more valuable IMHO than a squad of rock and rollers spraying lead and hoping to hit something.

    And for the civilians, it is over priced. A rich mans hobby. And the legalities make it not worth the effort, to me anyway. Whenever I hear about some Militia group or member being arrested for owning "illegal" machine guns I immediately think "set up". In all the years I was involved in the Patriot/Militia movement I never knew anyone who had a full auto. And every group I ever knew of cautioned it's memebrs to not even think about it. They knew that the feds were looking for any excuse to raid them and it was the hieght of ignorance to give them one.
  12. Quigley_Sharps

    Quigley_Sharps The Badministrator Administrator Founding Member

    Re: What's the diff between M16 and AR15 (mechanically & leg

    Last week end My wife and I went to a Gun Range near Eugene Oregon and rented 2 Tommy guns full autos and burned a bunch of 45 acp rounds.
    The smile on her face was worth every cent spent.
    If you havent shot one, you need to go try it.
    I wasnt in Nam in the Army, But I bet i fired 50,000 rounds several times over and a Few live Tow's,and a few 155mm
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