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

  1. #41
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    FWIW, I think the dual spring design of the KAC E3 extractor may play a part. Buffers don't really make a difference with this gun, it ejects the same with a carbine buffer and an H buffer. This is in spite of a noticeable difference in bolt speed. I've never had an issue with the gun that wasn't ammo related. In fact, the only issue I've ever had was with some really weak Centurion .223 ammo which short stroked regularly. It runs like a top on full auto with 5.56 ammo. Very controllable and slower cyclic rate than a Bushmaster M16 upper.

  2. #42
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    Quote Originally Posted by mtdawg169 View Post
    FWIW, I think the dual spring design of the KAC E3 extractor may play a part. Buffers don't really make a difference with this gun, it ejects the same with a carbine buffer and an H buffer. This is in spite of a noticeable difference in bolt speed. I've never had an issue with the gun that wasn't ammo related. In fact, the only issue I've ever had was with some really weak Centurion .223 ammo which short stroked regularly. It runs like a top on full auto with 5.56 ammo. Very controllable and slower cyclic rate than a Bushmaster M16 upper.
    If it's consistently ejecting that far forward under "healthy" conditions, then i'd say that yes, the dual extractor spring setup is a major part of that.

    Just out of curiosity, have you tried running the gun with a standard DI bolt in it just to see how it behaves?
    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

  3. #43
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    No, I've never tried a standard bolt. It's supposed to run with one if needed though.

  4. #44
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    Quote Originally Posted by mtdawg169 View Post
    No, I've never tried a standard bolt. It's supposed to run with one if needed though.
    Since i'm a "I like to see how different things work" kind of guy, i'd do it just for shits and giggles if for nothing else.

    See if a standard DI BCG displays similar performance indicators (such as ejection) or not, and also usibility indicators (controlability, etc.).
    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

  5. #45
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    Grumpy

    Out of curiosity, if you pull your charging handle all the way to the rear, is the bolt face even with or behind the back of the ejection port?
    And/or
    Is there wear on the base of your shell deflector near the back of the ejection port?

    I only ask because I have a BCM upper with PSA BCG and PSA receiver extension.
    No matter what buffer/spring combo is used the brass ejects forward.

    However it is not overgassed, the brass simply hits the back of the port/ base of the deflector, sending brass forward.

    Maybe thats not your situation, just another possibility.

  6. #46
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    Quote Originally Posted by saddlerocker View Post
    Grumpy

    Out of curiosity, if you pull your charging handle all the way to the rear, is the bolt face even with or behind the back of the ejection port?
    And/or
    Is there wear on the base of your shell deflector near the back of the ejection port?

    I only ask because I have a BCM upper with PSA BCG and PSA receiver extension.
    No matter what buffer/spring combo is used the brass ejects forward.

    However it is not overgassed, the brass simply hits the back of the port/ base of the deflector, sending brass forward.

    Maybe thats not your situation, just another possibility.
    I think this was intended for me. Mine has worn through the anodizing in the same area you describe at the rear of the ejection port / base of the deflector. Not sure where the bolt lines up. I believe the point where it makes contact with the deflector is what is causing mine to eject forward. This supports my earlier point that ejection patterns can be very misleading.

  7. #47
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    Quote Originally Posted by saddlerocker View Post
    Grumpy

    Out of curiosity, if you pull your charging handle all the way to the rear, is the bolt face even with or behind the back of the ejection port?
    And/or
    Is there wear on the base of your shell deflector near the back of the ejection port?
    FYI, the gun i'm talking about USED to be one of my guns. It was sold (not because of any issues, but rather I had a chance to get a different gun and I had to make trade-offs). And the current owner, a very good buddy of mine, is currently on a contracting gig so I can't just wander on over and examine the gun right now.

    That being said, by the time I sold it, it didn't have enough wear on the deflector to be able to tell you either way, especially since I used the A5 + xp spring after I figured out what was going on.

    Regarding bolt face location, when fully pulled to the rear, the bolt face came back to about 3/16ths behind the bolt catch, which is the critical dimension regarding that engagement and is what really matters. Any less then that and there's an increased chance for the bolt to outrun the bolt catch and not lock back on the last round, and more then that means that the nylon buffer is either too short or is degrading and is allowing excess bcg travel which could lead to increased fatigue of the action spring and excess wear on the internals.

    I only ask because I have a BCM upper with PSA BCG and PSA receiver extension.
    No matter what buffer/spring combo is used the brass ejects forward.

    However it is not overgassed, the brass simply hits the back of the port/ base of the deflector, sending brass forward.

    Maybe thats not your situation, just another possibility.
    In my experience, the incremental increase in weights from H buffers on up have very little effect in ejection in situations like yours, especially if the gun is running overgassed, and all other possibilities were ruled out (as in, did you replace your ejector spring, ensure there was no "O" ring on the extractor spring, etc.).

    I would venture a guess that you didn't try stronger action springs while experimenting, and if you did account for the ejector/extractor possibilities, then the fact of the matter is that depending on just how far forward your gun was throwing the brass, it was in fact probably over-gassed. If ejection was to the 2:30, that doesn't count to me as overgassed, FYI.

    For reference, We also tried an HK 416 buffer which weighs in at just about 5oz, and it had very little effect on the Noveske upper until we switched to the A5 with the xp spring. Even the A5 had little effect on it when using the stock action spring.
    Last edited by GrumpyM4; 10-02-12 at 00:28.
    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. #48
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    Quote Originally Posted by GrumpyM4 View Post
    Yes and no.

    Exact speeds? You're right. Pull out the do-hickeys and do-dads.

    Behavioral wise though, experience shows us that, once again, with all things being equal (appropriate milspec parts, springs, etc, that are still well within their expected life cycle) that the gun will behave in certian manners that give a good indicator of bolt speed being either within spec, or outside of it.

    As has already been established, under "normal" circumstances, indicators of out of spec bolt speed are in fact caused by other aspects such as worn action springs, ejector springs, fouling, loose carrier keys, etc. Meaning that simple parts replacement removes those false indicators and all is well because the bolt speed was never actually out of spec.

    But, when all of those other factors are accounted for and the gun is still behaving in a certian manner, it does in fact mean that bolt speed (i.e. the cyclic rate as you mentioned) is out of spec and other issues need to be looked at. Gas port erosion, incorrectly machined chamber/throat or excessive gas port size (if on a brand new gun), etc.

    I fully understand that all brass throw does under normal circumstances is indicate that *something* is mimicing either excess or under gassing, but it's a hell of a lot easier to know which end of the spectrum to start troubleshooting from by paying attention to ejection. That's all i've been trying to say this entire time.
    does extractor tension have an effect on ejection pattern?
    never push a wrench...

  9. #49
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    1. Bottom line there is no military specification for mid-length / intermediate length systems.

    2. Each manufacturer can use whatever HIS particular research, testing, or preference as an optimum compromise point. The GI carbine standard is the 14.5-inch M4/M4A1 or 20-inch M16-series shooting real military pressure M855 (or alternatively real M193) in a fat, chrome-lined GI 5.56 chamber -- no "Mild ammo", commercial bunny or woodchuck buster, or ammo surplussed by some third-world country or specifically made using cheap steel cases to meet WalMart customer demand for blasting fodder. What you state is vapor ware. Changing or swapping components is tuning to what YOU want. Nothing wrong with that, you just need to be aware that it is YOUR standard and no one else's. We live in America -- life, liberty, pursuit of happiness.

    3. Military specification doesn't care what the brass ejection pattern is. If it fires, ejects, and feeds the next round the systems works. The specs don't care if your brass is dented, the upper is dinged, or that your brass doesn't all magically land in a coffee can for you. 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?

  10. #50
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    Quote Originally Posted by mtdawg169 View Post
    Are you running the intermediate gas system?
    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.
    Gun and Gear Reviews- www.almosttacticalreviews.com

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