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Thread: Mk VII 50AE Modern Barrel Issue...

  1. #1

    Default Mk VII 50AE Modern Barrel Issue...

    I searched a bit and didn't see any posts about this issue... maybe someone can shed some light here.
    I bought a Mk VII 50AE Desert Eagle in 1993. I have shot it about 3000-3500 times over the years as it isn't exactly a plinking gun. The only issue it has ever had were caused by weakening springs or deteriorated extractor nub/spring. I can't say it has never failed, but it is extremely rare.


    So I bought a new 50AE Barrel with the intention of having a muzzle brake installed... I didn't want to modify my original firearm. I thought I better test it before having the work done, and to my amazement, it basically doesn't work. The symptom is failure to feed... empty chamber. Extraction is perfect, but it has never fired more than two shots in a row without manually racking the slide.


    I dropped my original barrel back in and fired 14 shots, mixing limp wristed with iron-grip in there, factory MR 300's and 350's perfect, as always. Even tried one of the new magazines and it worked fine, with my barrel. Dropped the new barrel back in, and converted it to an instant 1 or 2 shot max. It does manage to set the hammer without fail however, so the gas port isn't completely blocked or anything close.


    This issue got me looking around on the internet and have spent a few hours reading the horror stories of Desert Eagle pistols... while my experience is based on one firearm, it is more like a perfectionists love story. I know all about the issues that arise from grip, weak springs all around etc... but this issue is something I have no experience with.


    My questions might be...
    Gas port issue?
    Compatibility issue? (with early Mk VII 50AE)
    Bad barrel?


    I also bought a 44 Magnum barrel, which I have not fired yet... I will try it soon and see what happens... if I get many failures, I will assume there is something strange about this particular Mk VII.


    I am not a gunsmith, but I am a machinist. I checked this barrel very closely against mine and could find nothing different with most dimensions relative to function. The barrels are made completely different. My original is a two part barrel with completely different machining and the inlet gas port at 7 o'clock... while this new barrel is single part and 6 o'clock gas port.


    I think tomorrow I will take the springs out and cycle it carefully and see if I can feel anything dragging.


    Anyway, thanks to anyone who reads this and thank you in advance to anyone who can help. I am open to most any suggestions.


    MrBlackCat

  2. #2
    Join Date
    Jan 2010
    Location
    Near the Gila Mountains in SW AZ.
    Posts
    4,635

    Default

    MrBlackCat,
    The Desert Eagle is far out of my wheelhouse, so I'd just like to say welcome to the forums
    Regards,
    Greg
    [<a href=http://i43.tinypic.com/2n7fnux.gif target=_blank>http://i43.tinypic.com/2n7fnux.gif</a>

  3. #3
    Join Date
    Sep 2009
    Location
    Wet & Wild Pacific NW
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    27,932

    Default

    Ditto what he said for me too. I did get an intimate tour when they first came out at a sportsman show or maybe an NRA show in Seattle. The rep took it apart down to every single piece. At the time they only offered 357.

    It was a beauty to behold inside, very well machined. Wanted one ever since but never got one.

    I officially proclaim you our resident Desert Eagle authority. I'll keep watching to see how this pans out.
    http://bawanna45.wix.com/bawannas-grip-emporium#!
    In Memory of Paul "Dietrich" Stines.
    Dad: Say something nice to your cousin Shirley
    Dietrich: For a fat girl you sure don't sweat much.
    Cue sound of Head slap.

    RIP Muggsy & TMan

  4. #4

    Default

    Thank you for the welcome and replies gb6491 and Bawanna.

    Understandably, Magnum research says they can't do anything without sending the firearm, which I expected would be the case. I will just have to eat this one I suppose. I wouldn't even consider returning a near perfectly functioning firearm to have it potentially modified to work with a new barrel. The concern would be a change that might compromise the original functionality or compatibility with the original barrel.

    The next step is to try the new 44 magnum barrel and see if it suffers from the same issues. Part of me says I should just return the unused 44 Magnum set at this point. But it might tell me if this is some odd original tuning to this early model. I will be quite unhappy if I have to eat $800+ worth of pistol barrels as opposed to just $400+.

    Next I will try to dye the shell casings and see if the slide drag marks can tell me anything about how far the slide goes back.

    I will continue to update this as it might help someone else in the future, especially if a resolution is found.

    Edit: Another thing occurred to my while blowing through the gas ports on these... the modern gas port seems to have less volume, although I have no way to measure this. I wonder if between piston wear and dirty cylinder I get better pressure to the slide with my original barrel. I think I will try a new piston and see if there is any effect.

    MrBlackCat

  5. #5

    Default

    Double post for the purpose of separation of updates...

    Well, I got some 44 magnum ammunition today and tried the new 44 magnum barrel. Perfection, as the with the original 50AE barrel. I shot iron-grip to one handed limp-wrist... perfect. 200 rounds and the brass was stacked like firewood. (ok, not really, but it was extremely consistent.)

    Todays test session started by field stripping and bolt removal. I changed all springs, cleaned and oiled (super light, as usual) even though I am a couple hundred rounds early for service, and not experiencing any malfunctions with the original 50AE barrel, and the brand new 44 Magnum barrel. The cost of a rebuild kit is minor compared to the cost of ammunition anyway.

    With everything new, I loaded up a half dozen 50AE magazine and changed to the new 50AE barrel...
    I started with 350grain Magnum Research (Speer) loads. First shot, I iron-gripped it, and it fired and successfully loaded round two. Second round fired, and stove-piped round three. Cleared, iron-gripped, stovepipe, and variations of this for three magazines... enough.
    Well, this is a NEW problem anyway... at least the slide was traveling back far enough to scrape off another round.

    Long story short, the new 50AE barrel has not successfully loaded more than than one round. Determination... the new 50AE barrel has some substantial issue. I believe if this was a compatibility issue specifically with my firearm, the new 44 magnum barrel would have exhibited at least some of the issues.

    Maybe the port has a bit of something in it from the factory. The new 44 Magnum barrel is designed exactly like the new 50AE, so it isn't likely the barrel design change (compared to my original) that is causing the issue with my very early model 50AE, as I suspected earlier.

    I so wish I had another barrel to test... if someone is willing to rent me a test barrel, I will gladly do so. I am really curious about this now. I would like to believe I just have a bad barrel.

    If this was a ramp issue, an ejection issue or anything related to those functions, I could fix it... but if this is a gas port related issue, there is not likely anything a user can do.

    Next step will be to take this barrel to the test lab at work and see if I can devise a way to test the gas port flow... since I have a perfectly working 50 and 44 to compare to. If I can rule that out, then I can move on to "drag" maybe.

    I will also note that while I had the springs out of "everything" I tried a number of comparisons of "drag" relative to bolt engagement into the barrel etc... I was unable to detect any differences in the three barrels.

    One thing is sure... the new 50 AE barrel is not able to back the slide out far enough to operate properly.

    Update soon.

    MrBlackCat

  6. #6

    Default

    Update...

    Borrowed a co-workers Mk XIX 44 magnum which is a few years old (maybe 4 to 6) and the new 50AE Barrel was basically a single shot on it also. Exactly the same symptoms as my Mk VII... His 44, my new 44 and my old 50AE works perfectly on both guns.
    Something is wrong with this new 50AE Barrel...

    As of now, I have re-emailed Magnum Research to see if they will take the barrel back and test it without me having to return my perfectly working firearm with their not working barrel, then go through a gun dealer etc to get my gun back.
    Something tells me that if they get this barrel working on any Desert Eagle, it is going to work on mine.

    I will update this thread with the reply...

    MrBlackCat

  7. #7
    Join Date
    Jan 2010
    Location
    Near the Gila Mountains in SW AZ.
    Posts
    4,635

    Default

    Thank you for the updates!
    [<a href=http://i43.tinypic.com/2n7fnux.gif target=_blank>http://i43.tinypic.com/2n7fnux.gif</a>

  8. #8

    Default

    Quote Originally Posted by gb6491 View Post
    Thank you for the updates!
    Resolution or not, at least this can be available for others to find should they have similar issues.

    Well, Magnum Research won't test the barrel or take it back without my firearm.
    Ouch... a could have gotten a boat anchor for a lot less than $415! I don't really consider this standing behind your product.
    <sigh> I understand their stance a little bit, but apparently these guns CAN be a bit problematic, and because mine functions basically perfect with my original barrel, and the new .44 Magnum barrel, I don't want my gun modified, or even potentially modified, just to work with this one barrel that I consider defective. What if I got it back and it doesn't work with my other barrels? Magnum Research would have no liability and I would just be out my near perfect firearm. Another thing is that getting the gun/barrel working over a couple of clips of ammo is one thing... but what about over 1000 rounds? A gunsmith doesn't test that... they can't. No one rational would consider this, in my opinion. There is also potential mail loss, then retrieval from a gun store as they can't ship them back directly to you etc... I will just eat this one... and I won't be buying any more barrels for sure. The .357 was to be next if this went well... but. After I recover from $1000+ in barrels, parts and ammunition, I will just buy a modern Mk XIX in .357 Magnum, as it would have been tested for function, apparently unlike this barrel.

    Next steps...
    Because it seems the slide is unable to travel backward far enough to function properly, I will try to test for two things.
    1. Gas flow.
    Maybe the port is partially blocked.
    Maybe the cylinder is out of spec. (I checked this with calipers, but I will test it with higher precision)
    2. Drag.
    Maybe the chamber is binding the shell, taking momentum off the slide.
    Maybe the bolt lugs are binding against the barrel during unlock rotation.
    Maybe the sides of one or more bolt lugs are coming in contact with the barrel lugs.

    Even though the new .50AE Barrel is made quite different from my original/old .50AE barrel, I have it for reference. And I also have a perfectly functioning brand new .44 Magnum barrel for comparison, which is manufactured the same. I have to add that the .44 Magnum is SO nice to shoot on this platform... one handed rapid fire is very possible. I might go ahead and have a brake installed on the .44 barrel to soften it even more. I like to break my targets, not my wrists.

    Again, if anyone has any suggestions of why this might be failing, or additional tests I could try, please let me know.

    MrBlackCat

    Edit:
    1. Gas Flow...
    I don't have any pin gauges here at home, so I used precision calipers to check the diameter of each barrels gas cylinder...
    ~0.3957 (Original, should show some wear .50AE)
    ~0.3966 (New .44 Magnum)
    ~0.3984 (New .50AE)

    That seems like a lot more clearance for such a small piston/cylinder.

    Maybe someone can measure their Desert Eagle gas cylinder(s) and let me know how theirs compare...

    I am going to start leaning toward excess clearance in the gas cylinder... I will figure out a way to test this. I might grease the piston between shots for additional (though VERY temporary) seal.

    Another way I could test the slide in general would be to keep a little pressure on the slide lock and see if travels back far enough to engage with each shot... but I think it is clear the slide isn't traveling back far enough. Kind of sucks I used a new spring kit that I really didn't need to. I saved the parts though. At this point I have over $1000 in barrels, testing ammunition and test parts. At least the .44 Magnum works like my original barrel.
    Last edited by MrBlackCat; 02-13-2017 at 07:34 PM.

  9. #9

    Default

    Anyone have an opinion on modifying the springs to test for low gas pressure? If this were the issue, say from excessive clearance in the gas cylinder, then lighter springs would at least allow the slide to travel back a bit further, even if it wasn't able to put the slide back into battery.

    I have a set of old springs I could modify to test this... or what about removal of the inner springs I have read of?
    If this didn't help function, I would at least know to look elsewhere to try and resolve this.

    Any thoughts or suggestions would be appreciated.

    MrBlackCat

  10. #10

    Default

    Update...

    Been busy, but tonight I got a minute and swapped to an old set of springs I took out from a few years ago. A bit weak, at approximately 3/4" shorter uncompressed, than some new springs I have... but I took out the inner springs just to test it. It actually worked perfectly with my average grip... I didn't need an iron grip, and I didn't try limp-wristing it, but it worked perfectly for three magazines. I knew it was "close"

    So what next?

    1. Maybe that extra three thousandths of clearance on the gas piston is too much?
    2. Maybe something is dragging somewhere, defeating some of the slide motion?

    Again, any suggestions or insights would be appreciated.

    MrBlackCat

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