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Thread: What really fails on the AR?

  1. #51
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    Don't think I have ever broken an AR through normal use, at least not in the past few years. Have broken bolts, hammer pins, gas rings, gas tubes, through abuse (multiple C-Mag dumps, etc).

  2. #52
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    I broke a gas key screw this week.

    Rifle is a 16 inch with a carbine gas system. Has about 5000 rounds through it. Use it pretty hard at 3-gun matches and had it out a week or so ago shooting steel plates and this must have been when the screw broke. I have no idea where the head of the screw went. It must have gone out the ejection port or it fell out when I took the rifle apart. The rifle never malfunctioned. I found the broken screw when I took it down to clean it before a 3-gun match. Back up and running with a new screw. Just need to stake them both properly.

    It is a CMT BCG.


    Oddly enough, had a double feed with a barely used PMag at the match this weekend. Never had one of those before. Must be my week.





  3. #53
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    Quote Originally Posted by Iraqgunz View Post
    Just today while shooting the M4 at a large facility near Moyock, NC one of the Bushamsters had an issue with the "J" spring. The guys hammer pin kept walking loose every mag or so.
    I had that myself recently. I found the J spring was soft and "dead" as a piece of copper wire-- no spring to it at all. And unfortunately I've no idea where the hammer came from but it had been modified to AR15 from a 3-round burst hammer.
    Last edited by Ned Christiansen; 09-14-10 at 11:23.

  4. #54
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    Some of the Colt LE carbines are manufactured by Colt Canada - including barrels with the improved chamber. The gas system is the same thing - perhaps the gas port size is different.

    Not sure the carbine system is superior - but it works fine on the 16" for the Canadian military and a bunch of other NATO forces.


    Quote Originally Posted by Failure2Stop View Post
    And the C8 SFW is a different animal than a normal M4 Carbine based 16" barreled gun. It has a modified chamber and gas system, and I believe a buffer of similar weight to an H or H2, I can't remember for sure.

    I'm not sure if you were just poking fun or serious, but to be clear, to insinuate that the C8 SFW is proof that a carbine-length gas system with a 16" barrel is the superior choice is deceptive.

    Readers: check Colt Canada's website if you want, though it is lacking in detail, you can read what I am pointing out
    http://coltcanada.com/sfw-page.htm

  5. #55
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    Can you expound on that improved chamber? I'm curious as to the dimensions.

  6. #56
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    Quote Originally Posted by IndianaBoy View Post
    I broke a gas key screw this week.

    Rifle is a 16 inch with a carbine gas system. Has about 5000 rounds through it. Use it pretty hard at 3-gun matches and had it out a week or so ago shooting steel plates and this must have been when the screw broke. I have no idea where the head of the screw went. It must have gone out the ejection port or it fell out when I took the rifle apart. The rifle never malfunctioned. I found the broken screw when I took it down to clean it before a 3-gun match. Back up and running with a new screw. Just need to stake them both properly.

    It is a CMT BCG.


    Oddly enough, had a double feed with a barely used PMag at the match this weekend. Never had one of those before. Must be my week.




    Did you have to EDM it out??

  7. #57
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    Thought I'd throw in here, been an interesting year...

    -In the spring we had a bushy dump four or five rounds FA during a qual. The disco was only grabbing about .002 of the hammer, so when a round blew a primer, the now fired primer landed under the trigger nose which stopped the trigger from its full forward arc. It just so happen that where it stopped created a "Sweet Spot" if you will, where neither the trigger nose or the disco could reliably pick up the hammer. Ended up replacing the entire FCG, but a little disco timing could have avoided the issue all together.

    -Saw a gas tube mushroom wear down on a single side due to a combination mis-machined upper and bent tube.

    - Had a couple of hammer pins walking due to hammers missing pins purchased from unreliable sources

    - Saw a few bolts with lug shears or fractures

    - had a number of carrier keys either come loose or shear screws

    Outside of the normal issues we all see, most of the stuff I've been seeing has been related to poorly machined parts. On that note I've had a ton of bad LP gas blocks, lack of safety to trigger engagement, an unbelievable amount of mistimed discos, and two bushy detonations of unknown cause but more than likely bad ammo and a slew of minor gassing issues. Now that I think of it, we've seen a good deal of ammo induced issues this year.
    Kevin Johnson
    Johnson Tactical Rifles, LLC
    Pittsburgh, Pa

  8. #58
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    Let me see if I can remember.

    I've seen the little nipple on the buffer retaining pin shear off.

    Extractor's break, two I think

    Firing pin break, one that I recall.

    Carrier keys never staked coming loose.

    Disconnector springs working out.

    I've seen two or three trigger and hammer pins break in two.
    Sig Sauer LE Armorer
    Glock LE Armorer
    Colt AR15/M16 Armorer
    T.O.S.S. (Tactical Officer Survival School) inst. Tom Long
    Vicker's Tactical Pistol 1 & 2 Carbine 1 Advanced carbine Inst. Larry Vickers
    Intermediate pistol Inst. Ken Hackathorn
    Combat Speed Inst. Dave Harrington
    Performance Pistol Inst. Frank Proctor

  9. #59
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    Quote Originally Posted by IndianaBoy View Post
    I broke a gas key screw this week.
    Just a wild stab here, but I noticed the staking isn't what I usually see. Could the sudden vertical load (at an angle to the screw shank) have cracked the screw below the head? Would that be a worse load than staking the screw with pressure from the side rather than an impact?

    I'm assuming from appearances that this was staked with something like a punch rather than by pressure (like a MOACKS). Let me know if I'm off-base here.

  10. #60
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    I have seen several boogered up socket head cap screws, right out of the box, from reputable manufactures, Holo Krome, Allen and such. The broken screw could have a defect. If the underside of the screw was not flat and true the force of the chisel used for staking could have added a bending moment to a screw already heavily loaded in tension. The thing was probably right at the breaking point from the moment it was assembled. I don't see this assembly having much cyclical stress which could cause fatigue. However, a little bit of cyclical stress added to high static stress can cause fatigue.

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