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Thread: M16 SBR Problems

  1. #1
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    M16 SBR Problems

    To those of you who are pretty well versed in short barreled full autos here is my problem. I have an M16 lower with Safe/Semi/Full trigger pack. I have a 10.5" barrel w/ carbine length gas system. I cannot get it to reliably run, sometimes it will run fine for about 10-12 rounds before a double feed, sometimes it wont go 2 rounds before a double feed. It occurs on Auto and Semi, I have used about 15 different magazines, regular- H3 buffers. I for the life of me cannot figure out why it will not run right.

    Any help would be greatly appreciated.

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    What is the make of the BCG and upper and how many rounds through it? WHat brands of ammo have you tried? Are you using a suppressor? Also, have you tried using a new action spring?
    Last edited by Cincinnatus; 06-28-12 at 00:00.

    "Addressing the problem of shootings by ban or confiscation of non-criminal's guns is like addressing the problem of rape by chopping off the Johnson of everyone who DIDN't rape anyone while not only leaving the rapists' equipment intact, but giving them free viagra to boot." --Me

  3. #3
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    Quote Originally Posted by winfield813@yahoo.com View Post
    What is the make of the BCG and upper and how many rounds through it? WHat brands of ammo have you tried? Are you using a suppressor? Also, have you tried using a new action spring?
    Not sure on the make of the carrier, I assume its a Colt since the entire gun was bought as a Colt. Round Count is unknown, No supressor, and have used 3 different springs.

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    A true double feed is two live rounds trying to feed together. If it is a live round and an empty case you have a failure to extract or eject.

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    So is the entire rifle Colt, including barrel, upper, receiver extension, fire control group?

    Colt Carrier and bolt should be easy to I.D. Check your carrier key to see if it is loose.

    If not a Colt upper, who makes it? How many rounds does your rifle have through it?

  6. #6
    Dano5326 Guest
    if not knowledgeable enough to give accurate descriptors.. Pictures and video are your friend

    I was told a long time ago, the key letters in assume are ASS

    -a true double feed is a magazine issue.

  7. #7
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    since we are picking out particulars, I made a typo....its either a fail to eject or fail to extract. The upper is a built upper. The factory upper is a factory 20" Colt. It runs like a top with the factory upper. The 10.5 not so much. Using the same carrier and bolt in both uppers.

    Ammo used has been PMC 55 gr, XM193, Hornady Steel Match, M855 surplus. Same problem across the board

    I appreciate all the feedback thus far.
    Last edited by deadly0311; 06-28-12 at 01:38.

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    You need to increase the extractor tension. Use a Crane O ring on your extractor spring or an extra power extractor spring.

    I would also start with an H2 buffer.

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    Quote Originally Posted by deadly0311 View Post
    since we are picking out particulars, I made a typo....its either a fail to eject or fail to extract. The upper is a built upper. The factory upper is a factory 20" Colt. It runs like a top with the factory upper. The 10.5 not so much. Using the same carrier and bolt in both uppers.

    Ammo used has been PMC 55 gr, XM193, Hornady Steel Match, M855 surplus. Same problem across the board

    I appreciate all the feedback thus far.
    Firstly, picking out particulars is what is required here. This is a technical issue and technical issues require particular details to diagnose and solve the problem.

    It sounds like the 10.5 inch "built upper" is the culprit since the original runs fine. When you say a "built upper", please expand upon this. Did you build it? Whose barrel and upper receiver?

    I agree with Todd on the extractor and the buffer. If you are using a bolt group from a rifle length upper, you will need increased extractor tension in the form of a Crane O ring or a Specialized Armament Warehouse extractor spring.

    If your "built upper" was done with a bunch of suspect parts (ie not using Colt, LMT, Noveske, DD, or BCM parts) I would personally shit can the upper and buy yourself a Mk18 upper from either Noveske, DD, or LMT. They run and run and run. My LMT 10.5 has been boringly reliable. I recently put together a Noveske N4 10.5 with DD Mk18 rail; still haven't shot it but I expect it to be similarly boringly reliable. My two M16s are both set up with Colt M4 receiver extensions, standard carbine recoil springs, and Colt H2 buffers. They reliably run uppers from 16 inches to 10.5 inches. High quality parts from the above manufacturers will essentially guarantee that your rifle will run reliably.

    I would avoid using the same bolt group for both uppers. Buy yourself dedicated bolt groups for each upper (again using either Colt, DD, LMT, or BCM).
    Last edited by JoshNC; 06-28-12 at 12:33.

  10. #10
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    The upper was built with a DD 10.3 barrel, Troy lo pro gas block. Upper was a stripped Colt flat top we had laying around. We put a new extractor spring and o ring in there, running an H2 buffer and it runs fine.

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