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Discussion Starter · #1 ·
I'm chicken to take apart my 21e belt unit. Has anyone tried yet and videoed that? Just looking where to start. Looked for an ultrasonic cleaner but boy they are $$$$$$$$$$$. Like to have a nice clean unit after shooting. Any tips? I do have both calibers and it does seem that both cals are a little different. Who's up for disassembly?
 

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I have taken my 21E and 23E units apart multiple times. Its not too bad and I would rate it as similar but maybe slightly more difficult than disassembling/reassembling a burst pack. I would think that most folks who have the mechanical aptitude to disassembling/reassembling a burst pack could also successfully navigate a 21E/23E feed mech.

For the feed mechs, I look at it as two main separate sub-systems contained within the feed mech housing. There is the belt drive system and the cartridge follower/lift system.

The belt drive system that consists of the main drive shaft, sprocket, the control ring(s)/pawl(s), the pins/arms that interface with the slide.

Removing and reinstalling the belt drive parts is honestly pretty straight forward. There is a big C-Clip on the drive shaft in front of the sprocket that keeps the drive shaft in place and on the 21E there is a secondary drive arm that interfaces with the secondary (outer) control ring/pawl that also has a C-Clip that keeps this secondary drive arm/shifter in place.

On the 21E mech remove both the C-Clips from both the drive shaft and secondary drive arm/shifter. Remove the secondary drive arm pin and then start to push the drive shaft out of the feed mech. The 23E mech doesnt have the secondary drive arm/shifter as it only has one control ring/pawl (its similar to the inner control ring on the 21E) and it interfaces the slide directly as the 23E mech only advances on return stroke vs. the 21E that advances the belt on both the recoil and return stroke.

Once the drive shaft is clear the control rings/spring/pawls, the sprocket, and the secondary drive arm/shifter (on a 21E) will all come free.

The cartridge follower and lift system is much more of a pain to assemble/disassemble. While you can take the follower and lift system apart without removing the belt drive parts, you will never get it back together without the belt drive parts removed. There are a bunch of C-Clips along the feed roller follower pin that holds the feed roller follower, the sprocket pawl holder, the cartridge guide ramp lever, and the (I don't know what its called) spring loaded aluminum arm that only real job is to hold the cartridge guide ramp lever lift spring.

To start you can push in the aluminum arm that holds the cartridge lift guide spring in and free the cartridge lift guide spring. Next you need to free the tension on the elbow spring that lifts the feed roller follower. You will need a small screwdriver to reach into the feed mech from the top through the sprocket opening and push the elbow spring legs off each ledge of the feed roller follower removing the tension. (this is much easier if the sprocket is first removed)

Then start attacking the C-Clips along the length of the feed roller follower pin. I think there are four or 5 of them that keep all those parts separated along the length of the pin. Once the elbow spring tension is removed and the C-Clips are all removed, at that point you can start to slowly remove the feed roller follower pin from the feed mech going from back to front. Parts will start to fall out of the mech starting with the sprocket pawl holder assembly, then the feed roller follower and elbow spring, then the aluminum arm and finally the cartridge feed guide lever.

Going back together you just reverse the order you took it apart. The hardest part is getting the elbow spring arms back onto the ledges of the feed roller follower. Those elbow springs are super strong and your only access is via the top of the mech where the sprocket is. In my experience you can release the elbow spring with the sprocket still in place but you will never get them back on with the sprocket in place. You will need to make a tool out of an old small eyeglass type screw driver and make a little notch in the tip to control the elbow spring leg as you push it down and slide it back over onto the little ledges on the feed roller follower. The spring leg toward the front is the easier one to get back on as you have more access to get in at an angle. Getting the rear leg of the elbow spring back on the feed roller follower is the hardest part of the entire assembly/disassembly process and might involve some cursing. I do the back (harder one) first so there is no pretension on the spring to fight and then the front (with better access) one second.

There are a couple other bits you can remove like the slide itself, the slide bolt/spring, the slide return spring and slide return spring pin, the main feed mech pin, and the little lock lever for the feed boxes. They are held in place via a single roll pin or C-Clip.

I think the only part I have never taken apart is the actual locking latch itself. There is a very small roll pin that holds the main latch axle pin in place and a couple of spring and detents that should all fall out once the latch pin is removed. I have never had a reason or need to take the locking latch arm itself apart but it looks pretty straight forward.

Not sure if they helps or not and make sure you have a small screwdriver (or similar) with a notch in it to help get those elbow spring legs back into place.

Go slow the first time, take pictures, and keep all the parts in little containers so you don't lose a spring or clip and you should be fine. Maybe tackle the belt drive system first and get confident with taking it apart and putting it back together before taking on the cartridge lift system.

If you get stuck I am happy to try and help.
 

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Discussion Starter · #4 ·
Thanks a million... wait two million. Great detail on how to. I'll be sure to copy and paste :)
 

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Check these out- the smaller sizes aren't bad at all, price-wise and they make deep cleaning of convoluted assemblies like your feed unit a snap.

 

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Discussion Starter · #6 ·
Funny I was just looking at the ultrasonic cleaners. WOW $$$$$$ would like to get one to fit the HK21e receiver in ;)
 

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I use this one, pretty sure it would fit what you are wanting............ https://www.amazon.com/Hornady-0433...ocphy=1026201&hvtargid=pla-570606499148&psc=1
So you are putting complete barreled receivers in and also other parts like burst packs? Any lessons learned on “don’t do’s” with ultrasonic cleaning of HKs? I have considered picking up one of these, but have always been reluctant for fear of damaging an expensive gun.


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Thanks a million... wait two million. Great detail on how to. I'll be sure to copy and paste :)
No problems.

I don't know if I would recommend taking the feed mech apart after each range session to clean it as you are going to be in for an extended amount of time to take it apart and put it back together plus you always risk a small part getting lost in the process. (and there are "a lot" of small parts in there) Like a lot of gun parts there is also some concern about the wear a detailed disassembly causes as well, via punching out roll pins, flexing C-Clips, wear on pins and pin holes, etc. So I prefer to keep those detailed cleaning/disassembly to a minimum as you can do more damage over time via over disassembling/reassembling than you prevent with the detailed cleanings.

That said, for me I like to understand how stuff works, be able to repair it myself, and once every couple of years do a larger tear down to do a more comprehensive cleaning as well looking for any wear or problems before they become a potentially bigger issue.

I usually just clean my feed mechs in a parts washer filled with mineral spirits and a toothbrush. Then oil and grease after each cleaning. The good news is that the feed mechs have really good cleaning access from the bottom so I don't think you need to fully disassemble them on any regular basis.

I do have a Frankfort Arsenal ultrasonic cleaner that would fit a feed mech but have never really been a big fan of ultrasonics for firearms or firearm parts and really don't use it much.

Unfortunately, I have seen guns and parts damaged by over the years via ultrasonic cleaning. Sometimes those machines mess the part up in a single use and other time its a slower cumulative damage to the gun/part over time.

The only thing I would 100% trust dunking into an ultrasonic would be a solid stainless steel part (or something cheap I don't care about damage). I personally wouldn't put something as expensive and rare as a HK feed mech in an ultrasonic and have it potentially damage the finish, damage the plating on driveshaft or sprocket, or have water based ultrasonic cleaning solution stuck/left behind in the numerous little nooks and cavities inside a feed mech.

I personally wouldn't recommend putting an actual painted HK receiver in an ultrasonic unless you want to potentially refinish the gun. Just too many variables on finish type, solution, heat, etc. to know how its going to turn out.

Don't get me wrong, ultrasonics imho have their place in the firearm cleaning world. Especially for high volume,extra durable bonded finish, and/or inexpensive guns like duty Glocks. If you are a LE armorer and need to clean a couple dozen Glocks a week than dunking them in an ultrasonic that has the right pre-tested settings and solution confirmed from experience not to damage them is probably a good and efficient idea. Conversely, dunking a $7000 German HK21E feed mech in one, ehhh I would probably pass on that and stick to cleaning it by hand in my parts washer and as needed taking it apart every couple years to do a more more thorough cleaning.
 

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Thank you for this extremely helpful response, it confirms many of my doubts. The idea of dropping a barreled MP5 receiver into it for a deep clean was enticing, but no way am I going that route now. I’ll stick to what has worked and not damaged my guns. I’ll keep the ultrasonic for a limited set of cleaning tasks and away from my HKs. Thanks again.


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parts washer, rinse with acetone, lube.

easy
Thats where we ended up as well.
"Time to flood the crud", is what Dad likes to say when he throws the switch on the parts washer... followed by a thorough spray of Hornady One Shot cleaner/lube to all surfaces and parts. Done
 

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So you are putting complete barreled receivers in and also other parts like burst packs? Any lessons learned on “don’t do’s” with ultrasonic cleaning of HKs? I have considered picking up one of these, but have always been reluctant for fear of damaging an expensive gun.


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I never put/tried a painted barrel upper but have put several other parts bolts heads trigger packs etc even put my Registered DLO in, never had an issue I also use/used something similar to this forces the lube into place you could never get manually. And for what its worth I would never have hesitated to put a belt fed mech in. Just my nickel. Painted/aluminum/anodized I would be extremely careful with.........

 

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Painted/aluminum/anodized I would be extremely careful with.........
This is one other point of consideration with a HK 21E feed mech in an ultrasonic as well since in addition to the parkerized and plated steel parts there is also anodized aluminum in the feed mech as well.

If you do plan to use an ultrasonic on one make sure whatever solution, temperature, setting, etc. you do use is aluminum safe as well.
 

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which parts?
This feed mech part is anodized aluminum on both my HK German and MM feed mechs. This is the part that holds the coil lift spring for the 21E feed mech cartridge guide.

The MM part is a really dark blue/purple-ish color (think Sendra M16 color) where the German one is a dark gray (Colt M16A1 color)

HK21E STUD FOR FEED MECH NEW, GERMAN

Its only on the 21E feed mech as the 23E has a different cartridge guide lift torsion spring arrangement and doesn't use this part.

Bicycle part Tool Automotive exterior Auto part Composite material
 
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