Mk VII 50AE Modern Barrel Issue...

[MrBlackCat]

Update...

Got a new Spring Frame/Set, a new piston, and some other stuff.
First I checked the dimensions of the new piston... it is almost identical to my current piston in dimensions... maybe a few ten-thousandths, but nothing substantial compared to cylinder differences.

First test, I put my weakest set of old recoil springs back into the gun, but this time including the inner springs... again, the new barrel performed excellent for 14 shots. Enough for me to say "is working".

Next test, I put the new piston and new springs into the gun and loaded up 350gr this time. Wouldn't load these... it either failed to pick up the round completely, or grabbed the round between the rim and the case body for a stovepipe. I dropped my original barrel back on and it fired perfectly for another magazine of 350gr rounds.
I switched back to Hornady 300gr (because that is what was in the next two magazines) and the new .50AE Barrel. It was able to load the next round some of the time, even twice in a row once... but mostly fails to travel back far enough to pick up the next round.

As usual, my original barrel shoots every round without prejudice... the new barrel functions with my oldest, weakest springs and Hornady 300s.

Not sure what to think, but I am going to keep with it until I can figure out what is wrong, and how it might be resolved.

MrBlackCat

[gb6491]

MrBlackCat,
Thank you for the updates! They are an interesting read for me, especially so as I have very little hands on with the DE.
I would like to ask if you have looked for any differences (maybe to the point of using layout fluid) on the barrel surfaces that the bolt locks into between your different barrels?
Anyway, that's just a novice's thought; please continue with your updates.
Regards,
Greg

[MrBlackCat]

Hello Greg (gb6491)...
Thank you for the reply.
Barrel to bolt drag is something I have considered and is on the list. As hard as this barrel material (in my opinion it is very hard) break in would be really long term. This is pretty hard to locate and measure just because it has to be shot to see wear points/patterns reliably, but I do intend to try this.

So far what is "proven" is that the slide doesn't come back far enough to pick up a new round, most of the time... but I have yet to determine for sure if this is drag or lack of gas pressure transferred to the slide. I will continue testing.

One way to look at it, is that hard carbon does build up in the cylinder... which should decrease clearance/blowby in the cylinder. I just need to bore it out and sleeve it maybe.
One suggestion was to make a new piston a bit over-sized to fit the slightly larger cylinder. This is a consideration as this problem seems to be so close to the edge of functioning.

Unless I prove this barrel is out of spec in some way, I still don't hold any ill feelings toward Magnum Research... they wanted the entire gun back because the barrel is part of a system. My issue with that is that my "system" works perfectly under any conditions except with this new barrel.

Next: I am going to use a dental mirror and microscope to examine the inside of the barrel/lug area for burrs, and use dye and hand operation to look at contact points and concentrated pressures, then compare these areas to my existing barrel and see if de-burring is needed. I have to say... my original barrel shows a lot of sharp edges in this area still... after thousands of rounds... this is one reason I believe this barrel material to be a bit more hard than average.

On a side note, the new .44 Magnum barrel has worked flawlessly, from the first shot, with five different brands of ammunition so far. That is the Magnum Research I know and expect... now if we can just get this .50AE barrel working, that expectation won't be reduced.

MrBlackCat

[MrBlackCat]

Update...
Got a minute to try something else.
I found the lowest power/velocity rounds I have are the Armscor USA 300gr, at 1200fps. I fired them in my original barrel with no issue, as usual. I changed to the new .50AE barrel and it was unable to push the slide back far enough to load a round from the magazine. Actually the barrel was unable to get the slide back far enough to even eject the round... as expected.


So I decided to increase the gas pressure to the slide... I figured the best way to do this was to dip the piston in wheel bearing grease. Messy, but effective. It worked perfectly for one shot each time. It loaded the next round perfectly with the extra seal created by the grease.


SO... I don't want to remove the barrel and dip my gas piston in grease for every shot fired. I thought I might try to sleeve the barrel cylinder, but it is too close to the barrel diameter and the barrel material is very hard.


My plan at this point is to make a larger piston. I will do this by building up an existing piston, or possibly turning a new one. I will consider this a resolution. I will report back if this is successful.


Even though this is a resolution, I still wonder if the extra pressure is needed because of drag in the bolt area, or simply because too much gas is escaping due to the over-sized cylinder.


MrBlackCat

[MrBlackCat]

Update...

It will now fire any factory ammo I have. Is this good? Not really. Turns out my first suspicion was correct.
Because this thread has a lot of longer posts in it, I will re-cap as this is probably the end of the line.

The story, kind of like in Cliff Note form...
------------------------------------
New .50AE barrel failure to feed all but the hottest of factory loads, can't lock slide back, and even those 300 Hornady's were unreliable loaded.

Measured new .50AE against my old .50AE barrel... almost identical less manufacturing differences (2 part barrel vs 1 piece barrel)... EXCEPT for the gas port, which was about .003 (three-thousandths) larger on the new, malfunctioning barrel. Borrowed a co-workers few year old Mk XIX and had exactly the same result as with my own Desert Eagle. New barrel now doesn't function on two Desert Eagles... getting harder to blame issue on something with my gun.

So... tried new parts, old parts etc.
At this point I was able to verify that the slide was NOT traveling back far enough to function properly. Some video showed this EVEN when the gun did load a second Hornady 300gr, the shells didn't eject well compared to my original barrel with ANY factory ammo, lowest power to highest.
------------------------------------
Yesterday, I cleaned and dyed both .50AE barrels at the bolt receiver area and fired them. I inspected them both carefully for contact points and found them almost identical and nothing I consider unexpected or unusual.

The O-Ring...
So today I decided to go all out in the direction of "The damn cylinder is too large and out of spec" (yeah, I am not very tolerant of premium priced items with non-premium quality these days, so I am wearing thin here.)
Anyway... I stuck on o-ring on a new piston. Fired for 6 shots with just enough power to eject the shell onto my face, my hearing protection and sometimes roll off my hand to the ground, until the o-ring failed... this is with the Armscor/lowest power rounds I have, and new springs.

The Piston Build Up...
So I took the new piston and built it up in its flats and turned it back to .3915. So now I have a round piston, with no flat at its "rings" Risky? Maybe, but I know the gun well and was confident it could handle one time of bottoming out really hard if this was a bit too much. Well it didn't bottom out. It couldn't even load a second round. It didn't even come back far enough to catch a round between its case and rim to stove-pipe it! So I came in the house and found a couple of ways and formulas to look at gas flow with cylinder volume... those three thousands of extra clearance are too much area because of the pressures involved.
Here is something you can relate to... remember how boring out a cylinder .040 or .060 was enough to change the horsepower of an automobile at gasoline combustion engine cylinder pressures? Exactly... now consider the tiny percentage of diameter difference that .040 to .060 was compared to a cylinder around four inches in diameter.

The point... too much gas pressure loss due to in the cylinder to piston clearance is the problem with this barrel. So I built the piston flats up and brought it down to ~0.3945, then added some smaller flats back to it. (3-thousandths larger? Holy hell... I know) As calculated, it runs perfectly so far. It doesn't sound like much to have 3 thousandths difference, but if you look at the change in clearance between the piston and the cylinder, there is a 68% increase on the new barrels cylinder. That is a lot... and that is too much.

I would like to point out now, that this modified piston won't fit or even "start" in my original barrels cylinder. (I feel like I should type that part twice...)

Will this work?
Is this safe?

I doubt it... the welding would have compromised the hardening process of the piston, and I have no way of knowing what grade/type of metal it is. Even though the worst case pressures will not likely exceed what even mild steel can take, the stem is really thin.

I haven't gotten anywhere with Magnum Research just looking at the barrel without sending my gun, so I am going to try one more time with this information and see if they will have a look at it. This has become pretty straight-forward at this point... the barrel is out of spec.

MrBlackCat

[gb6491]

Thank you for the detailed up date, I admire your approach and method.
Here's hoping they just exchange that barrel with you. I too, dread sending my machines to anyone when I have the tools and skill to do the work, but lack only the parts they have.
Regards,
Greg

[MrBlackCat]

Thank you for the detailed up date, I admire your approach and method.
Here's hoping they just exchange that barrel with you. I too, dread sending my machines to anyone when I have the tools and skill to do the work, but lack only the parts they have.
Regards,
Greg

Thank you for the reply.
The fact that this barrel has the same issue on a another Desert Eagle should be enough for them to take the barrel back at least to check it. Maybe then, if it didn't have an issues have me send my gun in... which I would not have to do. I am fairly confident at this point that a simple check on their part to start with would have shown this issue. The MRI repair guys are going to know immediately what the tolerances are.

In my last email to Magnum Research about this issue, I sent them the cylinder vs piston dimensions and asked that they at least run these dimensions by someone in repair... I got no response. Not sure if they can't do this, or just have to assume that everyone is an unmotivated moron first. The latter being understandable these days it seems. As I said before, I would not even consider sending this gun anywhere... that option isn't on the table as the gun is in perfect condition, and the barrel isn't likely to function correctly on any gun they try it on.

Another consideration is that I sell the barrel for say half new with this issues and its history up front, to someone who isn't concerned with sending their firearm to MRI... then they will be getting a new barrel I can just about bet you.

I will try to talk with them again and see if they will consider taking the barrel back, if not, I will just have a bad barrel to figure out what to do with. Just because I can make a new piston that works doesn't mean it is a good or safe idea. Besides safety and function, I would also have to change the barrel and piston any time I want to change to my other two barrels. Dropping your piston in the field isn't the end of the world, I got spares, but dropping your CUSTOM PISTON in the field... yeah. Can I make another? Of course, but I shouldn't have to. This won't be the first time I have had a product be bad and then myself as the consumer, got to eat it. In their defense, MRI offered me an option... just not one without what I consider great risk and inconvenience.

MrBlackCat

[MrBlackCat]

Update...

Well this is positive. I sent a one page outline of the testing and results to Magnum Research asking them to reconsider testing the barrel without my firearm.
This time, there was a day or so delay in the response time... but it seems it might have been worth the wait. In my previous contacts with Magnum Research support, they wanted me to send my Desert Eagle in with the new barrel. Of course I didn't want to do this, but of course, they believed they would need my gun to see what the problem was. My main resistance to mailing my 23 year old Mk. VII .50 gun in was that it works perfectly and always has. It even worked perfectly so far, with my new .44 Magnum barrel. But I wanted a muzzle brake, so I bought a new .50AE barrel to have it added to as I didn't want my original gun modified. But the .50AE barrel doesn't cycle the slide.

This email was different though... I suppose it finally got to the right person, or maybe was thorough enough to be taken seriously. Here it is...
****begin paste****


By all means, please send that barrel to us to inspect. We will check it out and test it and if doesn't pass, we will replace it for you. While it is here, we can also install the muzzle brake if you wish.
You can send the barrel and a short note with the issue described to:


Magnum Research Inc
Attn: Customer Service
12602 33rd Ave SW
Pillager MN 56473


Magnum Research Inc.
Customer Service/Tech Support
Phone (218)746-3459
Fax (218)746-3097

****end paste****

Simple, clear, positive, and what I wanted to hear. I am still curious as to why this wasn't an option before I went to such great lengths to verify the cause of the issue. I am always glad to learn about new things, as I did with this "journey" of determining what was going on with this barrel. I am confident Magnum Research will find the same issue. The advantage will be that they already know the dimensional specs on the barrel. What took me around 10 hours total time to determine (swapping spring sets, making the new piston, test firing etc), they can probably know in a couple of minutes. My other disadvantage was that I suspected my gun being so old might have some other incompatibility. In fairness, it does say "Mk XIX only" on the packaging of both the new .44 Magnum barrel, and the .50AE barrel, and my gun is a Mk VII, although that isn't supposed to matter in the .50AE as they were to become the new platform anyway.

I will follow up again when I hear from Magnum Research.

MrBlackCat

[gb6491]

I imagine they deal with all types thus the send the whole thing in thing. It's heartening to read that once they realized you have some skills they adjusted the plan.
Please keep us advised on how this plays out.
Regards,
Greg

[MrBlackCat]

Update...


Magnum Research called today. My barrel is "within spec" and it seems there is nothing wrong with it. They asked for payment for installing the muzzle brake and they would send my tested barrel back to me. The only thing noted done was pretty standard... they polished the bolt lug area. Hmm... ok. Maybe I should ask to purchase their test gun... as it seems to be AMAZINGLY adaptive. (maybe the test gun springs had 5000 rounds on them?)


I will refrain from saying most of the negative things going through my mind right now.


The positive... the person I spoke with was polite, cheerful and listened to my entire statement of surprised distress as I explained to him a tiny bit about some of my journey to discover the over-sized cylinder issue. He listened a lot... and heard it. He just takes the calls and payments though. The only negative thing relative to our conversation was his statement of "if it doesn't function correctly I could send the gun in and they could repair it." (My thought was "that doesn't seem likely") If they don't even realize the gas cylinder was out of spec, they aren't touching my firearm. Now the 1% of potential of me sending my Desert Eagle in to be looked at, just became 0%.
(Damn... and this was a positive section of the post!)


So now I have a muzzle brake on a bad barrel. Great. A $450 boat anchor just became a $660 boat anchor... well, now its heavier at least. I suppose I need to get me a boat now.


It was kind of sad as the sales guy made a couple of statements that in my opinion shouldn't exist... the main one was something about how these guns generally like only one kind of ammunition. I quickly pointed out that my Desert Eagle didn't have this limitation, and never has. With statements like that, it does raise my sympathy toward Desert Eagle owners who claim to have experienced this. I have unjustly had a tendency to blame the individual, rather than the gun, because of my near perfect experience with my own Desert Eagle.


I suppose this thread has about run its course, as there isn't any resolution from Magnum Research. I am on my own from here on out.


The main thing I am saying now is "Thank GOD I didn't send my gun in!" Fixing the parts that don't need fixing is really sad. At least I dodged that bullet. (pun intended)


Oh well


Potential next steps...
Not sure exactly what I will do, but I will put the defective barrel in a drawer until I cool off for a few months as this has been a really negative experience for me.
A. I may learn a bit about the metal these pistons are made from and produce a couple of really nice ones to use with just this barrel. Sure leaves a bad taste in my mouth though. I will learn what I need to and do it right.


B. Sell the barrel to someone with this problem up front and get another, which isn't likely to have an out-of-spec gas cylinder... then they can send their gun in and play dumb and likely get a new barrel. I have a suspicion something I have experienced before might have happened. Sometimes people of one profession react poorly if they feel someone from another profession is trying to tell them theirs. Just speculation, but my thoroughness has brought this reaction from others before. As I stated before, I don't know the specification/tolerance of the gas cylinder to piston clearance, but I know math and logic, and obviously how to test it... and it worked. I don't have to be a doctor to know when a bone is broken. Again, I made a piston with the same clearance as my original barrel to piston clearance, and it worked... and the piston I made that enables the barrel to work, won't even fit inside my original gas cylinder. How do you even argue that?


While the money doesn't bother me that much, having something that doesn't work bothers me... now I am kind of leery of buying another Desert Eagle... especially if the modern ones are so inconsistent they can only work well with one particular round.


On a positive note, should I choose the new piston route, at least I can actually use the barrel with seemingly any round, like my original barrel.

MrBlackCat