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| | |-+  Miscellaneous Malfunctions with a "repaired" MDR
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Author Topic: Miscellaneous Malfunctions with a "repaired" MDR  (Read 1052 times)
ronaldparkerj
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« on: May 20, 2019, 06:58:23 PM »

So, I've been noticing a lot of intermittent issues with my "repaired" MDR and I thought I would reach out to this community to see what sort of issues you guys may be having. I've attached several images to show you the series of malfunctions that this gun has been experiencing. For a while the biggest one is ammo that normally cycles all of my other 308 rarely cycles this rifle, and often results in the bolt not fully returning to battery, but enough for the hammer to still fall. This is demonstrated with the picture showing the bolt carrier looking to be completely locked into battery with the hammer down. The other type of jam I experience frequently is the rifle jamming when releasing the bolt using the bolt release. This malfunction is shown in the picture with the case that has the two massive dents just below the neck. This jam is rather frustrating because it puts the case completely out of spec and makes it unusable. And then other jams consists of the rifle double feeding and miscellaneous failures.
All of this is with the new extractor and the new (2019) gas valve. Before these issues the rifle ripped off case rims to frequently, with multiple types of ammo, to get a read on what sort of malfunctions it experienced to most. The majority of my jams seem to occur suppressed while using the correct settings on the gas valve (using a Silencer Co Omega). My most recent trip to the range was successful unsuppressed with my reloads made a little hotter than normal and using CFE 223 instead of IMR 3031 (normally 41.5gr under 150gr FMJ). They were still within reloading specs (CFE 223 49.5gr under a 150gr FMJ), but just hotter than what I normally load. However, I also noticed some interesting wear marks on the brass as detailed by the picture showing the brass all laid out and the dents in them (when running suppressed). My primers look good so I don't think it was from over pressure, but I'm not 100% sure what caused this to occur. The pic with the case hanging out of the rifle is when I took the chute off thinking it was putting the dents in the case. I was wrong. I think it was the ejector.

I have reached out to Desert Tech about these issues and I feel like I am getting the run around. I keep getting told to "try this..." and "try that...", without any luck. They have suggested that the rifle may be undergassed, but it seems that they are suggesting that its just an "ammo" issue and not the gun.

You guys out there have any tips for me for how I can run with rifle without it screwing up?


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thehun
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« Reply #1 on: May 20, 2019, 07:11:22 PM »

Chamber is very tight on MDRs just FYI...like bolt gun tight...if you reload you might want to cast your chamber and see where your stands...with DT's inability to hold tolerances...this is what i'd recommend and reload accordingly...
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JesseJames38
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« Reply #2 on: May 20, 2019, 09:39:36 PM »

those marks you see in the casing are the ejector scissor hitting the side of the shell casing and pushing it into the ejector chute.   sorry to hear you are having issues with your new upgrade.  Makes me wonder what issues I will have with mine when it returns. Seems with the new extractor its taking more effort to push it out of the claw of the extractor.  Perhaps there are some burs on the claw its self.

Jesse
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kfeltenberger
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« Reply #3 on: May 20, 2019, 10:28:29 PM »

That brass is a *lot* dirtier than anything that's ever come out of my MDRs.  The first things I'd check are:

1.  Have you adjusted the gas valve settings?
2.  Are you using reloads?  If so, how does the rifle function with factory ammo?

If you're on the DT MDR Owner's Group on FB, contact Megan via PM.  Every time I've sent her a PM I usually get a reply within a few minutes to an hour, and if I catch it when it arrives, I can usually discuss the issue "real time".
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Kurt
ronaldparkerj
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« Reply #4 on: May 21, 2019, 09:34:48 AM »

kfeltenberger,
The dirty brass are rounds that were suppressed. My unsuppressed rounds are much cleaner. For 308, even factory ammo, I have found this to be the norm.

I have tinkered with the gas setting in suppressed, but found no change in the function. Megan did say that the Omega has low back-pressure so she said the "new" setting 3 could be used for suppressed use with that suppressor. I may just have to keep looking around for the sweet spot.

I am using mostly reloads, but get similar problems with PMC and Remington.

I have been in contact with Megan, but lately I've found when I suggest something may be wrong with the rifle that is when she stops responding to messages, which is very disheartening. The vibe I'm getting from her at this point is, "If it doesn't work, that's your fault."

How about the issue of the rifle jamming when releasing the bolt using the bolt release? Should I just be racking it back and not using the release?
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thehun
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« Reply #5 on: May 21, 2019, 01:14:30 PM »

Reloading puts another factor into the already experimental platform the MDR already is...
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CabbitOne
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« Reply #6 on: May 21, 2019, 08:00:41 PM »

kfeltenberger,
The dirty brass are rounds that were suppressed. My unsuppressed rounds are much cleaner. For 308, even factory ammo, I have found this to be the norm.

I have tinkered with the gas setting in suppressed, but found no change in the function. Megan did say that the Omega has low back-pressure so she said the "new" setting 3 could be used for suppressed use with that suppressor. I may just have to keep looking around for the sweet spot.

I am using mostly reloads, but get similar problems with PMC and Remington.

I have been in contact with Megan, but lately I've found when I suggest something may be wrong with the rifle that is when she stops responding to messages, which is very disheartening. The vibe I'm getting from her at this point is, "If it doesn't work, that's your fault."

How about the issue of the rifle jamming when releasing the bolt using the bolt release? Should I just be racking it back and not using the release?

Just for my own curiosity, what magazine(s) are you using?
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kfeltenberger
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« Reply #7 on: May 21, 2019, 08:23:14 PM »

I am using mostly reloads, but get similar problems with PMC and Remington.

How about the issue of the rifle jamming when releasing the bolt using the bolt release? Should I just be racking it back and not using the release?

I can't comment on Megan's attitude other than to say that she's always been pleasant and positive with me.  That said, given that DT seems to mention Federal American Eagle in some of their comments, I'd try that and see if you still have trouble.  Try it unsuppressed and then suppressed.  AE seems to be their baseline.

Regarding the rifle jamming with the bolt release, that is a new one to me.  I had issues with it jamming (last year when I first got them) just pulling the charging handle back and letting it go, but that was resolved as potential operator error.
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Kurt
ronaldparkerj
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« Reply #8 on: May 22, 2019, 04:23:51 PM »

The magazines being used are the Magpul 20 and 25 round magazines. However, I have noticed substantially more issues when the 25 round magazine is being used and now that I have cut back to the 20 rounds there are less problems.

I did have the opportunity to play around with the MDR and reload charges yesterday and did find that when using CFE 223 if I cut down on the charge I did get cases that were less beat up (the hotter rounds could easily be the culprit with that) and more reliable cycling.
If I recall on this range session, I had 2 jams out of 10 rounds (much better than my averages). 1 was something weird and I honestly don't recall what it was, and the other was a gas setting error on my part. Megan did suggest running in setting 3 while suppressed with the Omega and I ran it at 2. When I switched the setting to 3 it worked like a charm.

Also, in Megan's defense, she has been very helpful and respectful, but I am getting the vibe that from their perspective it shouldn't be having issues (which doesn't change that fact that it is). I think I just might have been spoiled by a recent warranty issue with Ruger (which was awesome!).

As I've further worked with the MDR I'm getting less issues, but the finicky nature of it does worry me sometimes. I guess I'll just need to keep playing with it. This platform has such amazing potential.
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thehun
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« Reply #9 on: May 22, 2019, 05:03:27 PM »

Do you have other platforms that use the same mags? If so...have you checked function in them?

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ronaldparkerj
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« Reply #10 on: May 24, 2019, 09:08:12 PM »

The mags I use are also used with my Aero 308 and a DPMS LR-308 (hopefully soon the Tavor 7). I normally have not had issues with those rifles using those mags, but the 25 round mags have been causing a kiccup or 2 in my Aero 308 lately so I have figured that some of the malfunctions are coming from the Magpul 25 round magazine.
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thehun
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« Reply #11 on: May 24, 2019, 09:21:32 PM »

Yeah. Stick to 20rd mags for .308...my rule of thumb.
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kfeltenberger
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« Reply #12 on: May 24, 2019, 09:34:22 PM »

I've used both 20s and 25s, though mostly 20s due to them being easier to shoot off a bench.  No issues to report, but then again, all the mags were new and unused until I got the MDRs.
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Kurt
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« Reply #13 on: June 09, 2019, 11:02:06 PM »

I'm wondering if your recoil spring isn't weak. I had some similar issues and replacing the spring improved it.

Polish the chamber if it hasn't been done already.
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ronaldparkerj
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« Reply #14 on: June 10, 2019, 11:13:37 AM »

I'm wondering if your recoil spring isn't weak. I had some similar issues and replacing the spring improved it.

Polish the chamber if it hasn't been done already.

So, I had considered the recoil spring issue, but, I may have found something else concerning. One of the jams seems occur when the mag release is used to load the rifle. This results in the case being shoved up against the feed ramps and chamber lugs and the bolt resting on the case body. Upon inspection of the point where the bottom of the bolt makes contact with the case, there seems to be a relatively small amount of "meat" or surface area. It looks as if the point of contact is small enough that any adverse condition, or movement that causes the bolt to "bounce" upward, could cause it to miss the base of the rim and catch the body or the angle of the extractor grove, which I think causes the jam that results in the case getting dents below the neck.
I have brought this to Megan's attention and at the moment she is working on getting me a paid label and RMA number. It would be nice to know if this has been the root of the problems.


* MDR Bolt and Case contact 2.jpg (63.55 KB, 1080x608 - viewed 49 times.)

* MDR Bolt and Case contact 1.jpg (52.71 KB, 608x1080 - viewed 47 times.)
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kfeltenberger
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« Reply #15 on: June 10, 2019, 08:14:17 PM »

Does this happen with all magazines or just one or two? 
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Kurt
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« Reply #16 on: June 11, 2019, 08:48:22 AM »

If I remember correctly, there was a question a while back about why the magazines sit so low and official explanation was that it was a compromise for 5.56 compatibility. I don't know why they didn't just exploit the magwell insert and conversion bar to adjust magazine height between calibers or if it even occurred to them to do so. Something else needing revision I guess.
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thehun
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« Reply #17 on: June 11, 2019, 09:57:45 AM »

That is awfully small contact area...
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JesseJames38
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« Reply #18 on: June 11, 2019, 10:57:22 AM »

I would also like to point out that the bolt .308 MDR is smaller then on a dome .308.  This also may have something to do with it.
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thehun
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« Reply #19 on: June 11, 2019, 11:11:17 AM »

Quite honestly...this is why I never bought into the whole multi cal platforms...compromises have to happen to accommodate different cartridges...
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