MP5 Clone Crushing Casings

ReluctantDecoy

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Here's a new one for me. My MP5 clone started having ejection issues. Gun would go "click" and when I pull the mag out a casing and a round would fall out of the receiver. Round would have the bullet crushed into the casing on the unfired round, leading me to think the spent round was getting in the way and the unfired round was crushing against the face of the chamber.

Replaced the extractor and extractor spring with a new brass one from HK Parts. Initially, it was going good, then last week this started happening randomly.

20191225_085041.jpg

I'm not even sure what part of the receiver it is crushing against, but these are mangled. Had like 4 of them in three different mags (2 curved, 2 straight). If it isn't the extractor or extractor spring, then what could it be? Ejector? I also noticed that this happens more often when I fill the prebans full. I've since been only loading to 20-25 rounds and that seems to help.

Anyway, as much as I love this gun, I also kind of hate the reliability. No flat nose and now this.
 

ReluctantDecoy

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what ammo? have you changed to a new type?
So far, has happened to Tula Steel 115g and Federal Champion 115g. I have some Fiochi 115g that I'm going to test this next weekend to see if it is just the ammo, but I seriously think there's a mechanical failure somewhere. While it's true that my clone likes the hotter stuff for proper ejection, I've never had it mangle a casing like before.
 

Wildweasel

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I would clean and lube and Inspect everything while you have it out, (you likely did that) and then Check the mags and clean them too and mag high inserted, If a mag is dragging on the bolt it can cause feeding/ejection issues.
Mine runs everything I put in it but then I built it and made sure everything was slick inside. I am running preban straight mags. I run mostly 115gr Tula steel also. (mostly so I don't have to chase down brass at the club.. )

Forgot to ask
what's your Bolt gap?

How many rounds down the pipe? If you are still breaking the thing in that may be part of the issue. (HK types can have burrs and bumps in the receiver that have to be burnished by shooting (Or manually cleaning up during construction. )
 
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ReluctantDecoy

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I would clean and lube and Inspect everything while you have it out, (you likely did that) and then Check the mags and clean them too and mag high inserted, If a mag is dragging on the bolt it can cause feeding/ejection issues.
Mine runs everything I put in it but then I built it and made sure everything was slick inside. I am running preban straight mags. I run mostly 115gr Tula steel also. (mostly so I don't have to chase down brass at the club.. )

Forgot to ask
what's your Bolt gap?

How many rounds down the pipe? If you are still breaking the thing in that may be part of the issue. (HK types can have burrs and bumps in the receiver that have to be burnished by shooting (Or manually cleaning up during construction. )
Thanks for the input. I don't recall the exact bolt gap measurement, but last time I tested it with a feeler, it was within optimal spec. I'm kind of anal with cleaning and lubrication, so I don't think that's part of it. After reading the link Supermoto sent (thanks, that's a great resource!), I am thinking two possibilities:
  • Ejector out of spec (didn't know how to previously check, but that link had good intel)
  • Locking piece is out of spec for SBR barrel (my clone original came with faux suppressor pinned on it)
I'm at least the second owner, so no idea of round count. I have probably 1,000+/- rounds through it. This latest issue seems to happen with both curved and straight pre-bans. The straight ones were new-old stock (date coded well into pre-ban era) which came wrapped in factory oil paper. Springs are still too stiff, but this issue still happens on the beat curved ones too.
 

ReluctantDecoy

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Huh...it only takes one short stroke or double feed to potentially ruin an extractor spring? I suppose it was a good thing I bought 2 when I replaced my last one then.
 

Wildweasel

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The SBR thing the standard mp5 locking piece should work then. 100 deg is stock, and for both the SMG Mp5 and the semi hk94 from what I can find. are you running a suppressor?

Ejector as long as it is close to the bottom of the bolt when you open the bolt (flip it over so you can watch ) and then open and close the bolt slowly so you can see the ejector track, it should follow the carrier to the bolt head and then up the slot and be very close to the bottom of the slot in the bolt head. (a small gap is ok but it must be past the edge of the bolt opening) adjusting the height can be done a few ways but it is not for the squeamish lol
 

ReluctantDecoy

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The SBR thing the standard mp5 locking piece should work then. 100 deg is stock, and for both the SMG Mp5 and the semi hk94 from what I can find. are you running a suppressor?

Ejector as long as it is close to the bottom of the bolt when you open the bolt (flip it over so you can watch ) and then open and close the bolt slowly so you can see the ejector track, it should follow the carrier to the bolt head and then up the slot and be very close to the bottom of the slot in the bolt head. (a small gap is ok but it must be past the edge of the bolt opening) adjusting the height can be done a few ways but it is not for the squeamish lol
God, I wish I could actually use that tri-lug for what it was meant for, but alas, I also live in MA. I had it transferred in with a horrible faux suppressor on it to meet length requirements. Made it a hell of a lot easier to deal with once my SBR tax stamp cleared. Just had to drill out the pin and remove it. Aside from length issues, who's buying these faux suppressors?

Thanks for the detailed ejector info. Will check later tonight.
 

Wildweasel

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I can take pics of mine if you need to see it but once you see it tracking you should be able to figure it out.
I may SBR mine it is so ugly with the 16" barrel. But I love shooting it.

I try to adjust them so they are as close to the bottom of the slot without rubbing. adjustment can be done a few ways and should have been set when it was built.

when you are building you adjust the height by either filing the tabs on the bottom of the receiver or add to them. (usually filling a little off if any. )
You can check the back of the ejector to see if it is worn or has been filed off. On my HK93 clone I actually made one from a G3 ejector and had to weld a little when I reprofiled it. (that is the other way to adjust the ejector file on the back or weld some on and reprofile. you try to stay away from that so the next guy won't have to deal with out of spec parts. )
 
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AKR

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The crushed round reminds me of what happens when you use a Galil mag in a .223 Valmet. The mag fits but does not present the round correctly to reliable feed in the valmet. I understand what you are experiencing is probably different but it came to mind. I have never seen that is a factory HK 9mm and I shoot my HK94 fairly regularly. Who made the gun? Have they stepped up to help?
 
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