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Thread: Do AR manufacturers "do" the mid-length differently?

  1. #51
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    Quote Originally Posted by Tzook View Post
    Yep. I'm definitely no expert on whether my gun is over/under gassed, but I don't notice any unusual ejection patterns and it seems to run everything like a champ.
    As long as it's running, you're fine. Especially if it is running well on lower powered ammo. I definitely fall into the "who cares where it lands" camp.
    Last edited by mtdawg169; 10-02-12 at 11:34.

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    Quote Originally Posted by sinister View Post
    3. ... Truly over-gassed would mean torn rims and blown primers (with GI ammo with crimped primers). Again, no mid-length MILSPEC. Even the MILSPEC is fairly generous in that typically only 1 gun in 100 is actually random-pulled and test fired for fit and function per drawings and specification package (and even if that one gun fails the tables specify how many other guns have to be pulled and tested before a lot is rejected).

    If a particular rifle or carbine ejects at the "Optimal" 3:00 to 4:30 angle through modification (Carrier Weight System, heavy buffer, spring, different loads) then is the system still "Overgassed" if the weapon cycles correctly?
    Yes. You won't rip off case rims, but you can still blow primers.

  3. #53
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    Quote Originally Posted by Gun View Post
    Yes. You won't rip off case rims, but you can still blow primers.
    Hang on a sec guys, how does an overly large gas port lead to blown primers? Tight chambers, I get that. But I don't understand how gas port size relates to a blown primer?

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    Quote Originally Posted by mtdawg169 View Post
    Hang on a sec guys, how does an overly large gas port lead to blown primers? Tight chambers, I get that. But I don't understand how gas port size relates to a blown primer?

    Oops, over pressured ammo does this, not super sized gas ports.

  5. #55
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    Quote Originally Posted by mtdawg169 View Post
    I definitely fall into the "who cares where it lands" camp.
    Who can seriously give a shit where it lands if it runs everything well?

    Worrying about a properly running weapon is like worrying about what color of FDE a weapon part is - a waste of time and energy that could be better spent elsewhere.

  6. #56
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    Quote Originally Posted by nineteenkilo View Post
    Who can seriously give a shit where it lands if it runs everything well?

    Worrying about a properly running weapon is like worrying about what color of FDE a weapon part is - a waste of time and energy that could be better spent elsewhere.
    Agreed. Others don't see it that way though, which is why I clarified my thoughts on the subject. My earlier comments about my own rifle were meant to be an example of why it really doesn't matter.

    The OP, asked if manufacturers used different specs for middies. The answer is yes they do, to varying degrees of success. I choose to trust the ones who have established a long reputation for turning out reliable guns, like KAC, BCM, Noveske or DANIEL DEFENSE. Not only am I confident that they have properly tested their barrel specs, I am also confident that they haven't sacrificed quality in order to hit a certain price point. In the end, going with a known quality manufacturer ensures you won't end up with an inferior product with bad port and chamber specs, both of which can lead to reliability issues.

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    Quote Originally Posted by ra2bach View Post
    does extractor tension have an effect on ejection pattern?
    It absolutly does.

    As an extractor spring is nearing it's cycle life, it weakens and doesn't push the spent brass out of the ejection port as fast.

    As I have mentioned several times in this thread, this is one of the symptoms that "mimcs" an overgassed gun, and when I say "All things being equal and using milspec parts", it also means that the ejector spring tension has been accounted for and is to spec.
    It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori

  8. #58
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    Quote Originally Posted by sinister View Post
    Truly over-gassed would mean torn rims and blown primers (with GI ammo with crimped primers).
    That's more of an out of spec ammunition or chamber issue then an out of spec gas system.


    If a particular rifle or carbine ejects at the "Optimal" 3:00 to 4:30 angle through modification (Carrier Weight System, heavy buffer, spring, different loads) then is the system still "Overgassed" if the weapon cycles correctly?
    Yes.

    That was one of the biggest complaints about the original ejection chart, and a complaint that I fully agreed with. That it suggested crappy aftermarket parts as corrective actions.

    If a gun has all factors accounted for that all springs are within their cycle life, and the parts are milspec, and it runs to the 3/4, then it's fine.

    Yea, I understand that mid-lenght gas systems are not milspec, but the optimal bolt speed doesn't change with the gas system. All that changes is how the gas system is modified to achieve that optimal performance given the change in the dimensions in the gas system and the benifits that longer systems provide over shorter systems, such as lower recoil impulse, lower pressures at the gas port, etc.

    If using milspec parts are used and are verified within spec (regardless of gas system length) and it ejects excessivly forward or rearward, it is either over or under gassed and bolt speed is not what it should be.

    If you go to aftermarket parts to "fix" this issue, the bolt can be brought to optimal operating speeds, but the fact of the matter is that those "fixes" are bandaids, and the actual cause hasn't been accounted for.

    WIll the gun run like this? Probably just fine for some time. But during that time, controlibility will be better, parts life will be extended compare to running it overgassed, and the weapon will handle a wider variety of ammunition and levels of fouling, while also causing less wear on the components of the rifle.

    p.s. And once again, I do not subscribe to the "chart", I use ejection as a secondary performance indicator as it should be, meaning that based on my experience, the optimal/acceptable ejection variation is somewhat different then the chart.
    Last edited by GrumpyM4; 10-03-12 at 02:49.
    It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori

  9. #59
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    Quote Originally Posted by nineteenkilo View Post
    Who can seriously give a shit where it lands if it runs everything well?
    There's a difference between "running", and "running well". Read the entire thread to understand the difference.

    My guns "run well". Many other folks gun run, but not as well as they'd like to think.

    Their choice though. No skin off my back.
    It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori

  10. #60
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    Cyclic rate with a perfect cycle of operation is the best way to tell whether an AR is properly working.

    Using ejection patterns is akin to measuring how much rubber my tires left on the ground and the exhaust emmisions to factor the top speed of my Vette or asking Miss Cleo vs. using a laser, radar or GPS to measure actual speed.

    Ejection patterns are far to easily influenced by extractor and ejector tension. Back in the day before stronger extractor springs for CAR gas guns and extractor enhancers we used to clip off 1/8" of ejector spring on match guns that would have problems because the ejector would overpower the extractor and allowing the extractor to release the fired casing too soon before ejection and would cause stoppages. This would make them eject forward after the ejector spring was shortened.
    Chief Armorer for Elite Shooting Sports in Manassas VA
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