MK760 Ejector Problems
- Thread starter idk508
- Start date
If you’ve already replaced the extractor and spring, and you’re still seeing stovepipes and FTEs, the ejector is definitely worth inspecting next. On a lot of these older MK760s, the ejector can get rounded off or worn down just enough to start causing issues
Here is a photo. Not sure about the specifications. When I replaced the extractor it became worse and wouldn’t even eject the casings.
Dumb question but how are you holding the gun when shooting it? Are you holding the mag? If so, don't. That can tip the feed angle / cause issues.
Did the gun ever run well? If not it could be a number of possible issues including that the ejector could be installed "off". I had a MK760 fixed and the culprit ended up being that the ejector was installed <5 degrees from aligned with the bolt.
That particular gun would run correctly if I applied upward pressure to the mag. I thought that it was a mag catch that left the mag too low. A gunsmith finally identified that the ejector was slightly "off". Gun runs great after he fixed the issue.
Did the gun ever run well? If not it could be a number of possible issues including that the ejector could be installed "off". I had a MK760 fixed and the culprit ended up being that the ejector was installed <5 degrees from aligned with the bolt.
That particular gun would run correctly if I applied upward pressure to the mag. I thought that it was a mag catch that left the mag too low. A gunsmith finally identified that the ejector was slightly "off". Gun runs great after he fixed the issue.
It never ran well. I only hold it by the gun itself.
The factory mag actually didn't work that well. It would only work when I held it upward. I bought a Suomi m31 mag, had some of the front trimmed down a bit, and it worked fine while only holding the gun, but still had failure to eject and stove-pipes.
I did not consider that the ejector could be bent. Every gunsmith thought the ejector was worn out.
Do you have any pictures of what your ejector looks like?
AdamsAutomatics
Member
Is your bolt locked back in this picture?? if so, it is further forward than the 2 MK760s I have here. Your ejector looks to be in decent shape as best I can see. The fact that it got worse after changing the extractor makes me wonder if the extractor you replaced it with is correct. You are welcome to reach out to me and I will see if I can help more.
No, I am holding the bolt back enough to show where the ejector is when near the bolt.
I do not see any obvious defects in your ejector, but your camera apparently chose to auto-focus on other nearby components, which adds uncertainty to the situation.
I suggest you start your analysis with the new extractor spring you installed. If you have a dial or digital caliper, can you tell us:
1. the diameter of the wire used to make the new extractor spring; and
2. how many coils of wire the new extractor spring has?
The original extractor springs I have encountered are not a common size. I have seen people replace the spring with a ready-made spring they found in a hardware store or online that was made with a slightly smaller diameter wire - only to find that actually made the jamming worse. Apparently, the design requires a strong extractor spring to firmly hold the fired case in position until it hits the ejector hard enough to be cleanly ejected clear of the ejection port. It seems that the smaller diameter wire of their ready-made springs was not strong enough for the job.
While you have the gun disassembled, the following additional information could be helpful in trouble shooting your situation:
3. close-up, high-resolution photos of the old and new extractor springs side-by-side;
4. close-up, high-resolution photos of the old and new extractors side-by-side;
5. measure the diameter of the wire used to make the existing recoil spring; and
6. measure the free length of the existing recoil spring in its relaxed state (out of the gun, lying on the workbench).
Regards
I suggest you start your analysis with the new extractor spring you installed. If you have a dial or digital caliper, can you tell us:
1. the diameter of the wire used to make the new extractor spring; and
2. how many coils of wire the new extractor spring has?
The original extractor springs I have encountered are not a common size. I have seen people replace the spring with a ready-made spring they found in a hardware store or online that was made with a slightly smaller diameter wire - only to find that actually made the jamming worse. Apparently, the design requires a strong extractor spring to firmly hold the fired case in position until it hits the ejector hard enough to be cleanly ejected clear of the ejection port. It seems that the smaller diameter wire of their ready-made springs was not strong enough for the job.
While you have the gun disassembled, the following additional information could be helpful in trouble shooting your situation:
3. close-up, high-resolution photos of the old and new extractor springs side-by-side;
4. close-up, high-resolution photos of the old and new extractors side-by-side;
5. measure the diameter of the wire used to make the existing recoil spring; and
6. measure the free length of the existing recoil spring in its relaxed state (out of the gun, lying on the workbench).
Regards
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i would also check the chamber to make sure no burrs, grit, caked in carbon is making it harder for brass to come out of chamber, you might try reisizing some fired brass, hold gun barrel down insert one in chamber, with receiver plug and recoil spring removed, drop bolt into receiver, turn gun level and with hand pressure pull bolt back, try several times to hand cycle the extraction process (maybe at varying speeds)to see if you can identify a problem. might have another hold and cycle gun while you watch election port
Hi. I know it’s been awhile and thought I’d give a bit of an update. I held the magazine (soumi m31 mag) and gave it a bit of a forward push while going full auto and it went through the entire mag, which was loaded to 35 rounds, without a single malfunction. The ejecting of the spent cases though still seemed a bit weak. The cases btw were cheap steel ammo.
I attached some footage from my GoPro. Unfortunately, the battery died when I ran better quality ammo through it.
I attached some footage from my GoPro. Unfortunately, the battery died when I ran better quality ammo through it.
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A couple of thoughts from the peanut gallery here:
It looks like you have two separate things going on here. On the first jam that occurs around the 12-second mark in your video, the fired case ejects nicely, but then it looks like the gun double feeds. Scott Andrey has a step-by-step procedure on his website of all the steps you need to take to properly fitting a magazine. If you are experiencing a double feed, going through all the steps of fitting the magazine may resolve it.
On the second jam around the 21-second mark in your video, I never see the fired case eject from the gun. Instead, it looks like the extractor lets go of the fired case before it ever gets to the ejector. On that jam, my primary suspect remains a weak extractor spring. If you can provide the photos and measurements I described above, we should be able to better get to the root of that problem and a probable cure.
It looks like you have two separate things going on here. On the first jam that occurs around the 12-second mark in your video, the fired case ejects nicely, but then it looks like the gun double feeds. Scott Andrey has a step-by-step procedure on his website of all the steps you need to take to properly fitting a magazine. If you are experiencing a double feed, going through all the steps of fitting the magazine may resolve it.
On the second jam around the 21-second mark in your video, I never see the fired case eject from the gun. Instead, it looks like the extractor lets go of the fired case before it ever gets to the ejector. On that jam, my primary suspect remains a weak extractor spring. If you can provide the photos and measurements I described above, we should be able to better get to the root of that problem and a probable cure.
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