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Discussion Starter #1
So I took a friend of mine to the range on Friday and let him fire my MKE SBR. He fired with no problems approximately 10 mags worth. I took it home and cleaned it for the next time I head to the range. Anyway, fast forward to Saturday night. I decided I had a little free time and went to the range. First mag, a single FTE. Seemed a bit odd, so I load the next mag in after clearing and start to fire. First one ejects, 2nd does not. I clear it, try again, same thing. Clear it, try again, this time, now it's not ejecting at all. I bagged it up and fired the AK for a bit. Once I got home, I broke it down and find the ejector spring able to be removed with just my fingers. I pulled it out and it's actually bent.

My question: Clearly they are parts that must be replaced from time to time, but is it *that* common? I didn't expect to have it fail and fail so suddenly (one mag to the next on Saturday evening). Guess it makes sense to build a small box of replacement parts and at least it wasn't anything major that failed.
 

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Very common. How many rounds through it? Always keep a spare around. You can try bending it back out some.
 

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I never leave home with out an extra HK extractor spring, one in the truck at all times (carry it with the universal cleaning kit excluding 17 cal that I carry all the time behind the seat) and some years a second is in the wallet on the back of the lawyers business card to call in case of a self defense shooting.
 

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The “legacy” extractor spring design employed in the earlier HK roller-locked weapons like the G3, HK33, and the 90-series rifles is BY FAR the weakest feature in an otherwise solid design. There is no over travel feature stop on it from being damaged. If the extractor is forced too far outwards (away from the bolt face) the spring is bent. If the spring is bent it is useless and must be replaced with a new spring. Bending the spring back “in shape” may work for a time in an emergency but it will fail again. The design was finally changed when HK developed the lever-style design with coil spring as seen in the HK21E, MSG90. This design has an “over travel stop” built into the extractor which prohibits over compression of the coil spring. The small rubber buffers in AR15/M4 bolts these days or the barrel extension pin in the HK416/MR rifles has the same function. HK could not easily add this new design to older legacy weapons as it requires a larger bolt head which means the barrel extension and receiver has to grow with it – very expensive change.

What pushed the extractor out of the bolt during operation and bending the spring is any obstruction in the barrel extension/chamber opening. This could be one misfed round or an empty case that does not eject and then get crunched back in against the barrel face. If this case/round lines up just right that obstruction forces the extractor away from the bolt face and the extractor spring is bent beyond repair/use – i.e. toast. This is why it is so common to see an otherwise reliable HK all of a sudden go to crap. Likely it occurs right after a stoppage and a bent extractor spring.

The copper-colored extractor spring is used in the pistol caliber guns. The gray or silver-colored spring is slightly larger in material diameter and thus stronger and is found in the rifle-caliber weapons. HK demonstrators use the rifle spring in all their MP5’s – I do as well. Why does the HK factory not use the gray spring in all pistol-cal guns? Well there have been one or two cases with very weak foreign ammo that the ammo recoil impulse will not drive the bolt far/fast enough to the rear and the extractor will not snap over the rim of the round during chambering. So install that rifle spring and test fire your gun with it with your ammo. In 30+ years I have never had this happen when using the rifle spring in the MP5.

ALWAYS have a spare extractor spring around! If you can reach through the open ejection port and easily move the extractor in the bolt head with your finger that spring should be replaced. You can watch the ejection pattern as well. When the spring is weak (“lame” the Germans call it) the weapon ejects more erratically and at less of a distance from the weapon. When in doubt replace it.

DON’T REMOVE the extractor for cleaning. TOTALLY unnecessary and it only damages the spring. Clean there when you replace the spring only. To remove the spring, lift up slightly with a pointed implement in the round section JUST ENOUGH to push it forward out of the extractor and off the bolt head. To PROPERLY reinstall slide the spring into in its correct upright orientation (as it will sit in the bolt head) until you meet strong resistance. Then place the bolt face on the table and rock it forward until the extractor spring “snaps” into place. Check for strong resistance and test fire.

In the “Navy” style trigger groups there is a cavity within the grip and HK sells a cap to cover that opening (to hold a thread cap or cleaning kit). That is a great place to store a spare spring or two so you always have it when needed.

G3Kurz
 

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Discussion Starter #5
Thank you very much for the detailed explanation. I don't remove the spring for cleaning for exactly the reason you mention - undue stress. I think I'll have to try my hand with the rifle springs and keep some pistol caliber ones on hand just in case.

Thanks again all.
 

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Just to add some helpful advice, you should get a little miniature tackly box and put together a spare parts kit. Especially if you're going to shoot an HK type gun frequently. It will make a lot of trips to the range more productive.

Not that you need all this stuff but I've just accumulated the following in my little tackle box:

10-15 extractor springs (gold tone and silver)
extractors (308, 223, 9mm)
locking pieces (various)
selector switches (for metal and plastic lowers)
feeler gauge
push pins, small and large
sling clips
sights
hammer springs
ejector lever axis pins
ejector lever springs
bolt heads (optional, I just collected them over time)

And various other things that I can't recall right now. A lot of this is predicated on how many you shoot and how often. Also, if you're not changing out parts on a sear pack like me, you'll not likely need a lot of stuff. But I'd definitely have spare extractor springs and maybe even a spare extractor for each caliber.
 

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Thank you "G3Kurz" for the detailed background with the explanation. I've had several people I consider to be very knowledgeable tell me to use the rifle caliber spring in my pistol caliber clones. Coming from someone at HK certainly carries much more weight. So I only have to stock two springs, the .40 caliber and rifle caliber springs.

Scott
 

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Thanks G3Kurz. A few years back I removed the ext. spring after EVERY outing until I read a comment from G3Kurz. I switched to rifle extractor springs & never had a function issue.
 

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I have a tiny roll pin punch that just fits the eye on the extractor spring, which I use to rotate the spring 90 degrees to remove when needed (i.e. bent or some other issue and suspected bent).

My box for just the little parts, have a tool box for for stocks, bolt groups etc. by caliber and the MM23eK gets it's own.

 

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Thank you "G3Kurz" for the detailed background with the explanation. I've had several people I consider to be very knowledgeable tell me to use the rifle caliber spring in my pistol caliber clones. Coming from someone at HK certainly carries much more weight. So I only have to stock two springs, the .40 caliber and rifle caliber springs.

Scott
You need only stock one extractor spring really. The rifle cal spring will also work fine in MP5/40's and MP5/10's. Try with your gun and ammo but we ran 1000's of these in FBI MP5/10's with no issues.

Ironically sometimes the rifle springs are cheaper than the pistol cal springs to purchase because HK Inc imports more pistol cal springs and each tiime they come in the unit price is higher.

G3Kurz
 

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You need only stock one extractor spring really. The rifle cal spring will also work fine in MP5/40's and MP5/10's. Try with your gun and ammo but we ran 1000's of these in FBI MP5/10's with no issues.

Ironically sometimes the rifle springs are cheaper than the pistol cal springs to purchase because HK Inc imports more pistol cal springs and each tiime they come in the unit price is higher.

G3Kurz
That is awesome news. I had never heard that. I'll certainly try it. The rifle springs are less expensive, especially if bought in bulk. If I only need one extractor spring that would certainly make stocking one much easier than two. It is too bad that it is so hard to get 10mm barrels. I think 220gr subsonic 10mm would be great subgun set up for matches. But I just can't justify the premium price for a 10mm factory barrel. I'd prefer a reverse stretch anyway. Maybe some day I'll spend the money. Thanks again for the tip about using rifle springs in .40 caliber. It is really great to have such a great resource here.

Scott
 

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As long as I'm going to order extractor springs, any other suggestions about spares to keep on hand for my MP5 clone?
 

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I carry a variety of spare parts as others have stated. I would have a spare extractor & ejector. Get a spare ejector spring in case you lose it at the range when changing the ejector.
 

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If you have a sear pack and are changing out the ejector between calibers, get an extra axial pin as these can get lost.
Soon or later will need a new roller retaining plate and best to get a couple roll pins in case one gets lost installing (they jump and hide ;-).
An extra set of stock and forarm pins might be handy if one gets lost when appart.

Like kwesi said the classic ejector and extractor are always a postive ...
 

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Discussion Starter #15
I went ahead and placed an order for various springs and pins last night. I have had a list going in my head for some time now, but the failure of my extractor spring at the range left me realizing that I need some on hand. Again, thank you all for the solid advice.
 

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So when installing the spring, do you line it up and push it in directly? Or does this damage/bend the spring before I've even gottena chance to use it? If thats the case, should I be turning it the final 90 deg to install it?
 

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So when installing the spring, do you line it up and push it in directly? Or does this damage/bend the spring before I've even gottena chance to use it? If thats the case, should I be turning it the final 90 deg to install it?
The armorers manual says you just line it up an push it directly in.
 

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Discussion Starter #19
As a follow up, I took the advice in this thread and grabbed a few various parts including a few rifle caliber extractor springs. Anyway, they were delivered Thursday and I had a chance to put a few hundred rounds through the the MKE today. Back to normal and running perfectly. :D
 

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You need only stock one extractor spring really. The rifle cal spring will also work fine in MP5/40's and MP5/10's. Try with your gun and ammo but we ran 1000's of these in FBI MP5/10's with no issues.

Ironically sometimes the rifle springs are cheaper than the pistol cal springs to purchase because HK Inc imports more pistol cal springs and each tiime they come in the unit price is higher.

G3Kurz
Hi G3Kurz

need help. the 40 extractor spring has a slight bend at the end part while the rifle extractor spring is just straight at the end. When i installed the rifle extractor spring on my HK German 40 bolt. the extractor was too stiff to move even with my two thumbs. tried charging a round into the chamber and bolt will not got to battery because extractor too stiff to chamber a round. any suggestions? thanks
 
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