Odd FTRB issue in 50ae

[jfa25]

Hello all,

Am having an issue with a weird FTRB issue that occurs with all ammo I use excepr for Underwood. Awhile back I sent my Eagle back to the factory for a “false reset” issue it was having. Before I sent the gun back in I ran about 600 rounds or so with maybe 2 issues the whole time. Got the pistol back and took to the range and ran Federal Fusion and Freedom Munitions and had a weird FTRB issue come up. It initially looked like a classic issue with the recoil springs when you just push the slide with your thumbs and it goes into battery. Mine wasnt like that, would have to drop the mag, pull the slide back and once the bullet dropped into the barrel i could close the slide. Seemed like the bolt would get stuck going into battery. Figured maybe it was a case of me limp wristing even though I never had beforehand. Took the gun home. Cleaned and looked at everything, all looked good. Had replaced the recoil springs and extractor nub at around 500 rounds so figured they were ok. Took the Eagle back out the next weekend, this time ran Freedom Munitions and Underwood Ammo, got the same issue with Freedom but ran Underwood flawlessly. On one shot in particular with the Freedom I held the gun as good as i could have, the barrel didnt even get to a 45 deg angle and still had an issue. Got home and cycled the gun manually with both Freedom and Hornady with no issues. This time decided to replace a magazine spring since i had one that came with the replacement springs package i ordered. Today went back to the range, ran Hornady with issues and once again Underwood ran just fine. I am not sure what it can be at this point. Maybe the gas system has issues? Figure if I was limp wristing that Underwood would be an issue too seeing how its the most powerful out of the ammo i have ran. Any ideas would be appreciated, thanks!

[MrBlackCat]

I wish I could get my hands on your gun... I know how frustrating this can be and the causes. In some cases, it is a combination of things.

It is very fixable. I have spare everything, so it only takes me a few minutes to figure these things out... but it is always simple. From many people you may receive many "absolutes" as to what is the cause, it then it only becomes probability their solution will be yours. Worse, from personal experience, listening to others got me a "partial fix" because it wasn't the cause, but some other issue (like extreme polishing of a given surface etc) allowed the "real" problem to work better. Then you have an even more obscure issue to find.

I am going to grab the calipers and see what brass the Underwood ammo uses and see if I can see anything there... All of my Underwood uses Starline brass. No issue there. I checked several boxes and saw very consistent chamfer.

If you gun isn't running well on Hornady, something is wrong with it though... Because you don't have a spare everything lying around, this might be a fair amount of effort to identify.

Traps...
The first time I started to experience failures to return to battery, I thought I needed springs, because that makes sense... but I have very seldom found this to be the case. You might need springs, but it isn't likely. I still use my original springs and spring frame for testing and it has over 3000 rounds on it. They ARE weaker, but function if the gun is extremely clean... 50 shots of target ammo and issues begin with these old springs because of unburnt powder particles in the frame/slide rails/springs.

Causes...
Is the ejector pin binding and the case can't seat into the bolt face enough to let the bolt lugs pass completely through to breech lugs? I had this happen a little, but it was causing cases to eject into my head. I had never taken my bolt apart back then and it was getting dirty and binding up. I was soaking the bolt in Hoppes #9 solvent back then but not taking it apart. You can't do that now as Hoppes will eat the polymer nub extraction spring up. Mine had the old metal coil type, so this wasn't an issue.

Is the Bolt Stabilizer pin bent or binding? I had that happen once, and reliability will go to hell. It bent because of another issue... I had re-finshed the slide and when I was cleaning overspray out of the bolt body cylinder and bolt stabilizer pin cylinder, I didn't do a very good job. Because the pin bound up, it actually bent. While it looks robust, it is VERY hollow where the spring passes inside of it. But if this pin is bent your will get unreliable results.

Is the Bolt Cylinder and bolt body moving freely? Under torque, this can be an issue.

Is there a carbon ridge accumulation at the front of the inside of the frame, on the plane where the gas piston exits the gas cylinder of the barrel? You shoot excellent ammo, so this isn't like the case, but shooting cheap 50AE, I get enough carbon build up to prohibit the slide from coming off without a running start... it looks like a casting seam eventually, and it so hard it is hard to tell it from the metal. I chip the mass out with a flat point screwdriver and then brush it out with Hoppes and a stainless steel brush.

Another thing I have seen after replacing the extractor spring/nub... in theory, if your gun is functioning as intended, as the bolt strips a new round from the magazine, it should stay firmly against the bolt face, sliding upward, compressing the ejector pin into its cylinder, and as the case slides upwards, the rim slips under the extraction claw... but if your gun is loading a little rough, sometimes the round will pop forward into the chamber rather than sliding up the face of the bolt. This causes the extractor claw to have to ramp over the rim of the shell... with a new extractor spring/nub, this can take a LOT of momentum off. Enough to cause failure to return to battery sometimes. Slowly letting the slide down on a round in the chamber is not recommended by Magnum Research (is in the manual not to do this), but I have always done it without issue and for testing of gun function without firing. In the past, I used to trim the wide side of my new extractor nubs just a few thousandths as they seem to vary in composition/density sometimes. (Age maybe?) What I do now is just polish the end of the extractor claw "ramp" area and I no longer have this issue with new nubs. It goes away fairly quickly anyway as the nubs break in and set well anyway.

Is this related to ammo? That is a good question, and from your experience it seems to be related... but how? I really don't know. I pound my 50AE with hundreds and hundreds of rounds of the cheap target stuff and I don't have any issue by unburned powder accumulation. I also have and shoot (in moderation) every factory ammo that was ever, and is made for the 50AE.

If I was able to watch your gun fail to return to battery, from the right angles, in slow motion, I could very likely tell what is happening. This has been difficult in the past however.
Worse case, you are welcome to send me your slide and barrel and I will figure it out. If not, it wouldn't cost you anything. This would be at your own risk of course, but I don't expect issue of course. If there is a problem with your gas system, (gas cylinder diameter) I do not sell or provide my custom gas pistons to anyone at this time... just to be clear. I shoot them in my guns and a couple of friends guns without issue for thousands of rounds in all calibers. It is just a liability issue. Gas system isn't like the issue as this would have been from the start.

I will help you try to figure this out on line as you seem to be willing to put a good bit of effort into your issue. I like seeing thorough posts like yours. I am willing to bet this is not going to be a huge deal, as the Desert Eagles are so robust, and other than the oversized gas cylinder issue with some US made barrels, I have not seen a Desert Eagle with an issue that wasn't easy to resolve, but identifying them can be a pain sometimes.

Example of complications...
I bought a .357 magnum barrel and bolt and it didn't function. FTF, FTE, random jams etc etc... in the end it was multiple issues. Factory bad ejector pin (too short), bolt face was too "grippy". Polished the bolt face and ended loading failures. Still failed to extract. Adjusted rake on extractor claw, polished the BACK of claw, that problem went away. Then it wouldn't eject worth a crap. My 10" 357 Israeli barrel didn't have this issue, but I thought that was because of the extra length... but I checked the barrel chamber, and it was simply too rough compared to every other barrel I had, including the 10" 357. So I polished that (Current production US made barrel)... it improved a lot, but ejections were still very weak. Finally I bought another 357 bolt and found the ejector pin on my first bolt was way too short. I had two frames to test on, so I could rule that out for instance.
Now I have a reliable .357 Desert Eagle... it was a pain, but worth it for me. This is just to give you an idea of why there might not be a one-stop solution. Either way, it can be resolved, and it usually doesn't cost much... and again, I will gladly "take a shot at it" if you will pay for any parts and test ammo.

If you do figure it out on your own, I would appreciate you coming back and posting the resolution... I am always curious.

Good luck!
MrBlackCat

[jfa25]

Thanks for the reply! I checked the ejector pin this morning and all seems t be ok with it. I also compared a spare gas piston i have with the one currently installed. In terms of “wiggle room” in the gas port of the barrel they seem to be identical but would need calipers or something to really know for sure. I have had two gas pistons break on me hence the need for a spare. As of right now I basically have two options, send back to Magnum or maybe running my barrel on my buddy’s Eagle and see if I get the same issues. Either way will report back what either I find or Magnum finds.

[MrBlackCat]

Interesting... never had a piston fail in any way. I still run my original Israeli gas piston in my MkVII 50AE with over 4000 rounds of 50, and about a thousand more of 44, and 357 each.
I have always wondered what causes gas piston failures... I have seen others report them breaking. I have actually built up gas pistons with weld and turned them down on a lathe to a different size and run them without issue for many hundreds of rounds. I just make them from stock now, but the point is that even those test pistons I made have never shown any sign of failure. Maybe the hole in the frame is too small for the piston shaft and doesn't allow for enough alignment slack and them keep impacting the gas cylinder chamfer. I really don't know what could be causing it. If I had a gun doing that, I would super-clean it and dye the piston and cylinder and cycle it a few times and see if, where, and how hard it was hitting. Could also be some material defect, but that would not be likely to happen twice.

Trying a barrel on another gun is a great way to test... if your barrel causes the same with the other slide, bolt, and frame, maybe try the other guns barrel on your gun and see what happens. At least you can narrow this down to a group of components this way. If it is a little bit of multiple things, it can be a bit more complicated, but still, I am sure it can be resolved. My experience with Magnum Research repair is small, but dismal, so I resolve Desert Eagle issues myself. Everyone doesn't have this same experience of course.

Breaking gas pistons, RTB failures... maybe they are related. I have read of this, but as I said, I have no experience with it.

I can tell you this... in some ways these guns are quite tolerant... I bought a new slide and built it up as .357 Magnum and after some early testing, I found out it is warped... about 14 thousandths of an inch end to end. It shows up when I dye the rails when I was testing it early on. I measured it with a feeler gauge on a precision surface. My other two slides (Israeli) are perfectly flat.

Anyway, I hope you get it worked out soon.

MrBlackCat

[jfa25]

Received my Desert Eagle back on Monday. Gotta give credit to Magnum Research. Was only one week from when i sent to when i got it back. They replaced the bolt stabilizer pin and put they adjusted the gas piston. The piston looks brand new though so am guessing they replaced it. Was able to take it out tonight and run 20 rounds of Hornady and 20 rounds of Freedom Munitions without any problems. Thanks MrBlackCat for the suggestions!

[MrBlackCat]

That is great they got it functional again... this is a common pattern if you read on Desert Eagle forums. If you send it back, sometimes takes twice, they will almost always fix it. (I will note again this was not my experience, but most people seem really satisfied with service from Magnum Research)

Makes sense about the stabilizer pin. You can get unground stabilizer pins if you want to grind it yourself and change the bolt rotation timing... I keep a couple of the unground ones myself. I am guessing something was in question there. Might be custom ground, or maybe your original was a touch out of spec.

If anything comes up, or your reach a good round count without issue, please share your experience again.

MrBlackCat

[CPTKILLER]

That is a pain!

Glad that it is working.