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Discussion Starter · #1 ·
I've had my DJ Getz MP5's for 2 years now. While I absolutely love them, Navy and K, I've gone through a few extractor springs. I'm on my 4th for the Navy, and just dropped my 2nd in the K. While I did get a few extra extractor springs from Getz, they're the copper variant.

I'm looking into the rifle extractor springs for the guns. Are they truly better than the copper springs? And is there a difference between the HK91 & HK93 extractor springs? Thanks in advance
 

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Teufelshund Tactical
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It is always difficult to give recommendations for HK factory products when dealing with clones, because there are obvious differences.
From HK, the copper colored extractor springs are for the 9mm SMGs. The silver colored extractor springs are for the .40 and 10mm SMGs and all the rifles. There is no difference in the sliver colored springs.
Some people choose to run the sliver colored extractor springs in all of their weapons, but HK specifically recommends against this in the K models. With the K, the bolt is lighter, moving faster, and the distance traveled in recoil and back to battery is less. Having more tension on the extractor can prevent the empty casing from clearing the receiver and the next cartridge being properly chambered in the proper amount of time, resulting in the extractor being caught out of position and thus bending the extractor spring back. This is a greater concern when firing the K on full auto or suppressed and worse still, when fired on full auto and suppressed.
Generally, though, if you are noticing a significant wear/damage to internal components, and failures to fire and eject, especially with clones, it most often points to the timing being off and needing to address that specifically. Sometimes that can be swapping out internal bolt group components to get the bolt gap into a better range. Other times, it requires the barrel to be pressed back in, as it was possibly not correct from the start.
 

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Discussion Starter · #3 ·
Marine0303 I bought them both new directly from Getz, as rifles. Now they're both SBR's. While I don't have a round counter, my guesstimate is I have about 2k through the Navy, and 1k on the K gun. And I have a can (TiRant 9) that I've used on both.
When I first started to have a problem, he took the Navy back cleaned it up, explained that the MP5 requires frequent cleaning and specific areas to focus on. He also told me about the extractor issue in the roller locked world, as well as changing out the extractor spring. He gave me a few to take home.

After that I would always take the extractor and spring out to thoroughly clean the bolt. Is there a possibility that I could have damaged or increased the wear on said springs? How can I check if there's a part that's out of spec?
 

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Yes. Every time you take the extractor spring out, you reduce the amount of tension it puts on the extractor. It's basically something that you need to leave in place unless you are planning on replacing it. You don't need to clean under the extractor every time you clean the weapon; it's a deep-cleaning only practice, once every several thousand rounds.

I put in a gray extractor in my SW5 (fullsize MP5 clone) and have not had any issues since. My Zenith has the copper spring, but I'm planning on replacing that one with a gray extractor too once it wears out.
 

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Teufelshund Tactical
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As mentioned, removing and replacing the extractor spring places significant wear on that relatively fragile part.
It is not required to remove the extractor spring for regular maintenance, but when you do remove it, HK recommends it be replaced with a new one.
 

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Discussion Starter · #6 ·
Ok, that gives me a lot of insight. After Getz changed the original extractor spring, I'd took the extractor and spring out to clean each time. Going off what you guys said, there's a good chance that's was happened to extractor spring #2 and #3 in the Navy, and probably helped to kill the K gun spring.

In regards to cleaning was Getz correct about the frequency of cleaning?
 

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From HK, the copper colored extractor springs are for the 9mm SMGs. The silver colored extractor springs are for the .40 and 10mm SMGs and all the rifles. There is no difference in the sliver colored springs.
It is my understanding that there are three roller locked extractor springs, that I know of. The copper colored one https://www.hkparts.net/shop/pc/Extractor-Spring-For-HK-MP5-94-MP5K-SP89-9mm-5p55.htm for 9mm. The steel colored one https://www.hkparts.net/shop/pc/MP5-40-10-Factory-Correct-Extractor-Spring-7p409.htm with the bend in it for .40 caliber. And the straight steel colored one with the same shape as the 9mm https://www.hkparts.net/shop/pc/HK-Rifle-Extractor-Spring-For-All-HK-s-German-8p188.htm is for rifle calibers both 5.56X45 and 7.62X51. "G3Kurz" works for HK and has posted that all roller locks "could" use the rifle spring but that the rifle spring in the pistol caliber guns would tend to cause more extractor wear.

James, you are far and away more knowledgeable about HKs, especially roller locks than I. What you posted about the copper springs and the K guns makes sense and I'll have to get some copper colored springs for my replacement parts box to use in my 9mm guns. As far as checking the extractor spring, my method is pull the cocking tube support handle until the face of the bolt is toward the back of the port in the receiver. Reach in with my finger and try to pull the extractor towards the port, away from the center of the bolt face. If I can move the extractor with your finger, the extractor spring is no good and I replace it. I only remove my extractor spring if it doesn't pass my finger pulling test or I am having extraction issues and I need to clean under the extractor. Which would be holding an empty shell casing and putting it on the bolt face, shaking the bolt holding the shell, the bolt falls off. It usually has taken a couple of thousand rounds of use before I would need to clean under the extractor. I have ruined a brand new spring installing it into the bolt. I have found it is so easy to ruin an extractor spring by removing/installing it. YMMV.

Scott
 

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Doesn't the method of turning the extractor on its side to relieve the pressure before removing/installing result in less damage to it?
 

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Ok, that gives me a lot of insight. After Getz changed the original extractor spring, I'd took the extractor and spring out to clean each time. Going off what you guys said, there's a good chance that's was happened to extractor spring #2 and #3 in the Navy, and probably helped to kill the K gun spring.

In regards to cleaning was Getz correct about the frequency of cleaning?
I typically clean my clones after every range outing, especially if I'm using a suppressor, but this is definitely not necessary. I just do it to prevent excessive amounts of carbon from building up in the trunnion and on the bolt head. I haven't really shot a ton of rounds through my clones without cleaning, so you might have to ask someone more experienced about that. But from what I've seen, you would only need to deep clean once every several thousand rounds.
 

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Doesn't the method of turning the extractor on its side to relieve the pressure before removing/installing result in less damage to it?
If you twist the spring, you are forcing one side down. It has been a long time since I have pulled an extractor spring and tried to reuse it. As James stated above, HK recommends installing a new one. Personally, I would rather change the spring at my work bench that at the range. When I install a new one, I push it straight in instead of turning it. I made a little tool to remove the spring using a broken 1/16" punch. The end is small enough to go into the center of the spring loop. I ground a depression just behind the end to catch the diameter of the spring wire. It grabs the spring better than the smooth surface of a new punch.

The last time I bought springs from HK Parts, I bought 25 rifle and 25 .40 caliber. Since "G3Kurz" had said that the rifle springs could be used with all the roller locks. I tried a rifle spring in a .40 caliber. The gun was a Coharie Arms with a RCM bolt replacing the original MIMs. The wire was a little too high on the very end of the extractor spring. So I had to file it a little to get the bolt inside the trunnion. So I ordered some .40 caliber springs so I wouldn't have to mess with it. All my 9mm RCM bolts came with new HK copper colored extractor springs. The next time I buy parts, I'll get some copper colored 9mm springs. YMMV.

Scott
 
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