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Thread: The Desert Eagle Gas Cylinder...

  1. #1

    Default The Desert Eagle Gas Cylinder...

    The Desert Eagle gas cylinder... from sarcasm to solutions, this is a first hand look at the dimensional variation and potential effects of these variations on the function of the Desert Eagle pistol.


    The intent of this writing is to possibly aid in troubleshooting a problem pistol. If nothing else, should you have trouble with a Desert Eagle, you could use this information to rule out a high-tolerance gas cylinder as part of the issue.


    First off… a picture is worth at least 1000 words… so have a look at 14 barrels I currently own…



    # Barrel Length Diameter
    1 Israeli 6 50AE 10.00mm
    2 Israeli 6 50AE 10.01mm
    3 US 6 50AE 10.11mm
    4 Israeli 6 429DE 10.00mm
    5 Israeli 6 44Mag 10.06mm
    6 US 6 44Mag 10.08mm
    7 Israeli 6 41Mag 10.02mm
    8 US 6 357Mag 10.06mm
    9 US 6 357Mag 10.05mm
    10 US 10 50AE 10.08mm
    11 Israeli 10 44Mag 10.05mm
    12 US 10 44Mag 10.02mm
    13 Israeli 10 41Mag 10.01mm
    14 Israeli 10 357Mag 10.02mm


    Although I live in the US, I used metric measures because of the higher resolution.
    Even with the relatively low precision of calipers, have a look at the numbers relative to each other and you will see where this is going pretty quickly.


    Jumping straight in...
    Barrel number 1 is my very first 1993 Mk VII 50AE barrel. It has over 4000 rounds through it at this point. With this barrel and its gas cylinder dimensions, you will never understand the term “limp-wristing” because it doesn’t happen… this is mostly due to optimal (proper?) gas cylinder clearance, between the piston and cylinder.


    Barrel number 3… the third barrel I bought. I wanted a muzzle brake on a 50AE barrel, and didn’t want to modify my original barrel, so I bought this barrel for that purpose… but it doesn’t work well enough to bother using. I have posted about this in other threads, but long story short, it has been back to Magnum Research twice and I am told it functions fine and is within spec. The point being that if you have this issue, you are probably on your own. They must test these things in a vice, with dynamite for ammo is all I can figure.
    With barrel 3, some functionality can be achieved with the hottest of rounds, locked elbows, and the muzzle brake helped, probably by keeping the gun more flat.
    However... before I retired this problem barrel, I produced a custom oversized gas piston to bring it to the same clearance as my original barrel/piston, and it works perfectly with the oversized piston. The custom piston I built for this barrel is so much larger it will not fit into any other barrel I own. But somehow this is within spec... whatever.


    With barrel 3, an example of the degree and type of failure... with weaker (is there such a thing in 50AE?!) ammo like Armscor, Precision One, and American Quality, the slide often doesn’t travel back far enough to get behind a new round, and ends up between the rim and case for an instant stove pipe about half the time. Most of the time it closes on an empty chamber because it can’t even pick up a new round. Not fun at all… but within spec. I’m no gunsmith, gun-builder or firearms manufacturer repair center, so who am I to say it’s out of spec? It couldn’t be! It must be something else, like me limp-wristing or holding it wrong right? It isn’t like I have more barrels in the same caliber, multiple frames now, multiple slides and bolts, and even someone elses loaner frame to test with is it?
    OH WAIT! I have all of the above, but only one set of elbows and wrists, so it must be those. But the issue magically goes away when I have either of the two other 6” barrels (#1 and #2) in 50AE that show not a single sign of issue with substantially less clearance in their gas cylinders and don’t need custom built gas pistons to function.
    I will end the rant here... lets just be clear that you are on your own if you end up with a barrel like this and don’t buy your ammo from a dynamite manufacturer... but if you know this is your problem, at least you won’t pull your hair out figuring it out, in case you don’t have different frames, slides, etc to test with like I do.


    Barrel 6… Now lets guess which other barrel has issues with lower power ammunition... you didn’t have to guess it was barrel number 6 in 44 Magnum. I also run a custom over-sized gas piston for this barrel… until I retired it like the 50AE. It wasn’t as problematic, but it was weak... how do I know? Because 4 brands/loadings of ammunition that would not cycle in barrel 6 work flawlessly in barrel 5. I guess nobody told barrel 6 it was within spec either… Dang, this is kind of hard to argue that one too. Or ordered some new less-limp wrists and a manual on how to shoot a Desert Eagle though. When they come in, I should be able to use this barrel without issue. (Ok! Ok! I’ll try to turn off the sarcasm, but I don’t own a boat for these anchors I keep paying for.)


    Barrel 10… Yes it has a higher clearance, but this barrel doesn’t really have an issue even without a custom gas piston. This is because it is longer. If you have 6” and 10” barrels, you will probably already know that the longer barrel allows for a longer gas pulse, so slightly weaker rounds can often be used reliably. If you have rounds that barely run in your 6” barrel, they will usually run in a 10”.



    Keep in mind that gas system clearance is only part of the picture in reliability. As I stated earlier, it is worth checking out, even with the relatively low precision of common calipers, it can show up. Gas piston clearance is worth ruling out.


    Another common question I get... is relative to gas piston diameter consistency. The pistons I bought this year are within a few ten thousandths of an inch of my original 1993 piston. I have not seen out of spec gas pistons before personally. My original gas piston has over 6000 rounds of 50, 44, 357, and a handful of 429’s now. (note, I do not make custom gas pistons for others.)


    How you hold most any automatic pistol can have an effect on function of course. If death-grips and locked elbows allow me to shoot cheaper or lower powered ammo, I understand why and what is going on. But the point of this post is that the gas system CAN be far enough off to be the CAUSE of malfunction, so “Limp-Wristing, it might not be your fault…


    I have read and been given suggestions on what I might be doing wrong to cause malfunctions... but from my perspective it is just a case of accidentally putting a poor quality barrel on.


    “Maybe that Israeli gun just doesn’t like US made barrels…” I put my Desert Eagle through some sensitivity training and it didn’t seem to be the issue... My Desert Eagles (multiple now) don’t seem to be racist at all actually. They do seem a bit biased against over-sized gas cylinders however. Maybe there is some training for that too.


    I hope the effort of sharing my path to function can help you get your Desert Eagle running as they are very capable of... reliably… but it is also important to understand that in some cases, regardless of what you might be told by those who are paid to know, there is some chance that problems with your Desert Eagle might not be anything you are doing wrong or any wear part you can replace.


    Good luck, and happy shootin!


    MrBlackCat

  2. #2
    Join Date
    Jan 2010
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    Near the Gila Mountains in SW AZ.
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    Another excellent, comprehensive post MrBlackcat! I don't own a DE, but can appreciate the effort you put into this.
    Thanks!
    Regards,
    Greg
    [<a href=http://i43.tinypic.com/2n7fnux.gif target=_blank>http://i43.tinypic.com/2n7fnux.gif</a>

  3. #3

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    I also read through your post here.

    Interesting information.

    I took the following measurements off my U.S. - made barrels (seamless between barrel and barrel extension, no longitudinal grooves) for the heck of it.

    BAR3576MC: 10.02mm
    BAR446MC: 10.00mm
    BAR506MC: 10.05mm

    BAR35710MC: 10.05mm
    BAR4410MC: 10.05mm

    I haven't had a chance to bring my pistols to the range yet, though - so I couldn't really report on function.

    Any chance you guys would know where I could get a .50AE 10 - inch barrel in Matte Chrome (BAR5010MC) with the Weaver rail on top, minus the longitudinal flute on the sides?



    Or any other finish in this form, for that matter (I'll probably have it refinished by Ford's Custom Guns)?

    I wouldn't mind getting a whole DE5010 pistol for the barrel

  4. #4

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    If an excessively wide Gas Cylinder was the culprit, would letting it accumulate carbon fouling improve function?

  5. #5

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    Quote Originally Posted by The Glockodile View Post
    If an excessively wide Gas Cylinder was the culprit, would letting it accumulate carbon fouling improve function?
    Yes to some extent... the down side is the increased friction and once it gets a few thousands thick, it will flake off and cause issues. The piston enters the cylinder at random angles also, so beyond a certain point the scraping of the softer carbon surface starts increasing the tendency for failure to return to battery. If you think about it like this you will see why accumulated carbon the cylinder hurts more than it helps... in that LAST little bit of travel, the slide needs enough momentum to rotate the bolt into place... and at this point in motion, your springs are almost back to their point of least pressure, and the bolt has made contact with the breech face, and even the bolt stabilizer pin/spring is pushing back a minute amount.
    It doesn't seem to build up much on cylinder with low clearance. I have polished a couple of mine to see if it helped reduce carbon build up, and it does, but not a significant amount.

    MrBlackCat

  6. #6

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    It's this part, and where the spring assembly attaches to the slide, which seem to be the pistol's Achilles Heel...

  7. #7

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    If I read your other posts correctly, less than 0.0025" to 0.0030" of clearance between the piston and gas cylinder is ideal?

  8. #8

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    Quote Originally Posted by The Glockodile View Post
    If I read your other posts correctly, less than 0.0025" to 0.0030" of clearance between the piston and gas cylinder is ideal?
    Yes... with the normal size vents (those flats on the top and bottom).

    You can have more clearance on a longer barrel because the gas impulse is longer than a 6" barrel. I don't know how much more, as this is hard to quantify.
    I do know that if you have a round that ALMOST cycles in a 6" barrel reliably, and you have a 10" barrels with the same piston clearance, it will usually function in the longer barrel fine.

    MrBlackCat

  9. #9

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    Seems like the the pistol should have been designed with a slightly wider gas channel, or a longer gas cylinder - if they couldn't keep things tight.

    Perhaps they never anticipated the production of neutered magnum loads going mainstream, a la current 10mm loads.

  10. #10

    Default

    Quote Originally Posted by The Glockodile View Post
    Seems like the the pistol should have been designed with a slightly wider gas channel, or a longer gas cylinder - if they couldn't keep things tight.

    Perhaps they never anticipated the production of neutered magnum loads going mainstream, a la current 10mm loads.
    I agree... more gas volume for a more tolerant firearm.

    The Israeli's don't have issues keeping the cylinders to spec to this day though... and they were the original manufacturers.

    I never owned a gun like a 357 Magnum back in the 80's to know how much they changed... but there are many 357 Magnum rounds produced today that can't open the slide of a Desert Eagle enough to clear the case length from the chamber. That is why I like letting people shoot Buffalo Bore 125's in mine just to show them "how far the 357 Magnum has fallen" (sorry for the drama there, but it IS true). 1700+ FPS from a 6" barrel. That is what 357 Mag is about...

    I have a project of re-chambering a Desert Eagle barrel to 10mm Auto, as fully loaded (hunting rounds) lap into the 357 Magnum Zone for muzzle energy, at just slightly higher pressures. I am pretty confident will work. I have a modified magazine and bolt I a got working (manually) before I got the tooling to rechamber/bore/sleeve a barrel. I have everything I need but time.

    MrBlackCat

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