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HK21 HK23 beltfed host - questions

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Looking to add a belt fed as my next sear host if not purchasing a complete registered receiver gun or gun already with a sear. Any reason to go with one type of host over another. Initial instincts want me to find a host with a DLO trigger box.  Appears lots of different manufacturers from Fleming, Volmer, TSC, Michael’s Machines and more. What I want is a HK21 with parts to go to HK23 config and any extras to make my experience better. What are the must have accessories? What does the collective wisdom of the Sturm board suggest? Any things to avoid? What are the values of the various guns from different manufacturers and why do some demand a premium?

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To swap calibers around you’ll need to get the E series. 

The 21/23 use a special ejector lever and the trigger box needs to be clearanced for it. I wouldn’t want to go cutting on a DLO box to do that. 

I have a Beltfed Precision Products (BPP) 23EK and it runs great. Now that being said I have close to 30 hours in making it work as it had some issues right out of the gate, but now.....yeah it runs 100% flawless and eats anything I feed it. The EK has a shorter shroud so I can run short barrels in it if i wanted.

Must have-spare Barrel, SAW adapter plate (for the feed mech so you can use M249 SAW sacks to feed ammo) bipod, and at some point you’ll wanna get a tripod for it. You will also need to make sure your stock has the tripod mounting studs on it. Original tripods can be expensive but MG3 tripods can be found for decent money. With an MG3 tripod you need a couple adapters to make it work, which Ralph at RDTS makes. 

All in all I’m very happy with my host. That being said if i hadn’t fallen into it for a steal ($7,500 but not working) I wouldn’t have bought one as its hard to justify the $12k-$14k they bring new. Parts are not cheap and getting harder to find, however the guns are built like tanks so it’s sort of a non issue. 

I’m looking forward to getting the roll/light bar done so I can mount it on my Jeep Gladiator....it will have a mount in the center so I can put my 23EK on it :-)

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If you're doing an "E" that's a  4 position trigger, generally not compatible with a DLO box unless it's redone.  Sear is a better option IMO.  I have a spare converted MG3 tripod available since I got an HK tripod a while back should you take the plunge.  Fortunately I've not really had to deal with any of the builders, other than some small stuff. 

The guns are not built like tanks, they are finicky, break parts, are expensive, and time consuming to have fixed if you have to send it out.....like a Ferrari.  With guys making clones there are more parts today than a few years ago.  The bad news is quality seems second to original HK parts which are now very scarce and command very high prices when they show up.

Had a Fleming 21EUG which was done on a ptr receiver, broke a lot of parts.  New 21E is all German with a sear, but I don't shoot it. I would like to get a 23 conversion set but nobody seems to make parts that replicate German 23E parts for some reason?   Rather shoot an MG42 because parts are a small fraction of the price and available. HTH

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Posted (edited)

At a high level there are two types of “HK21”s belt feds out there.  

The original/older version is the “HK21”.  This is the gun with feed mechanism housing that wraps around the G3 receiver and is welded in place.  The  star drive feed mech itself then slides into the welded on feed mech housing and locks into place.

The original HK21s are in 7.62x51 only (although TSC did make a small number of 5.56 conversions) .  To load these guns the belt is pulled through the feed mech using a loading tab so your access to the belt feedway is very limited so clearing  jams, etc. can be more problematic.   The HK21s only advance the belt as the bolt carrier closes.  The original HK21s were only are designed to run off non- disintegrating DM1 belts vs. links.

The original HK21s also have a shorter shroud compared to the more modern guns.   The original HK21s have a bit of a reputation of being not the most pleasant shooters in the world with excessive recoil.

Original 21s were built by many of the older names who are no longer in  business Fleming, Vollmer, as well as gunsmiths who are still active today, Michaels Machine, TSC, RDTS, Terry Dyer, and there are plenty of home built guns over the years using imported FMP parts kits.

The other variant is the updated HK  “E” series  Hk21E and Hk23E.  (there is also an HK21A1 and 23A1 in between but these are pretty rare)

The E guns are distinct from the older HK21 guns in that the feed mech swings down from the receiver.  This makes the loading operation different in that you swing the feed mech down, load the belt and then snap the feed mech back up to the gun.  (you can also load it via starting tabs by pulling a belt through the feed mech as well) .  The E guns have the longer shroud (in factory spec form) in comparison to the original 21s. (Although there are non-HK-factory “K” variants of the E guns with short shrouds and correspondingly reduced length barrels)

The E guns can shoot either 7.62x51 or 5.56x45 via a caliber conversion kits that consist of a caliber specific barrel, bolt carrier group, and feed mechanism.  They can also go from belt fed to mag fed with caliber specific mag fed conversion kits.

The E gun advances the belt with both the recoil and closure stroke of the belt in 7.62x51 increasing its belt pull capability over the older version (the 5.56 E kit only advances the belt on closure), the E guns have an upgraded buffer system, upgraded clubfoot stock, different barrel latch safety mechanism, and are designed around a 4 position 3rd burst fire control group.

The 7.62 E guns can also run belts or links and there are different generation feed mech sprockets and bolt heads designed for different belts/links.    The factory E guns have a completely different full auto sear in that the sear and sear trip are all one piece and the bolt carriers have a completely different style trip on the bottom to engage this different sear arrangement.

There are basically two flavors of E guns in the marketplace.   All German built guns that were built off a HK91 receivers and use all German parts from a demilled German E gun and the American clones using US made parts built by either Michaels Machines or Beltfed Precision Products.   (although there are some mixed US/German part guns out there as well)

In terms of cost/desirability:

At the bottom of the pack are the older original HK21s.   Guns built by a reliable builder like RDTS on a German HK91 receiver and parts command more vs. somebodies home-brew creation using FMP or unknown origin components.   These original HK21s exist in both registered machinegun receiver as well as semi auto form.

The semi auto versions of these guns usually run around $8 to $10K or so and the RR versions around $30K.

In the middle tier:

Original Hk21 style guns that have been upgraded with various E parts.  These guns may have the E buffer system, E shroud, E Stock, been tuned to run links vs. belts, etc.   but still retain the classic welded on feed mechanism housing of the original 21 design.  These guns exist both in registered receiver form as well as semi-auto.  Depending upon the upgrades these guns are usually in $10K to $15K range and the registered receiver versions around $30 to $35K.

US built clone HK21E/23E guns by MM or BPP.  These guns have the swing down lowers, caliber conversion capability but are designed as semi autos and to work with a friction sear.  As a result they  have a different bolt carrier designed to work with a friction sear, also have a hybrid barrel latch safety system,  and the 5.56 bolt heads use full round rollers vs. the half moon style rollers of a German 5.56 gun.   The US Clone guns run around  $15K (for one caliber) and the conversion kit is usually another $5 to $7K.  So say $20K+ range  for both 7.62x51 and 5.56x45 kits.

At the top of the cost heap are the German built E guns.  

These exist in both registered receiver form as well as semi-auto.   For the most part these guns have been built by Michaels Machine, TSC, RDTS, and Terry Dyer.  There may be others out there (Gerard Miller who did work for MM)  but most of the all German E guns I have ever seen for sale were made by one of those guys.

The semi-auto German E guns will be pretty close to a factory E gun but will have modified bolt carriers in order to work with a friction sear (transferable sear or box).  These all German semi-auto E guns are $30K and up depending upon which caliber(s) kits they come with , accessories, condition, etc.

The registered machinegun receiver based guns that were built off a HK91/G3 RR and full German 21E/23E parts kit  are going to be the closest you can get to a factory HK21E/23E.  They will take all factory parts, use the factory designed E sear system.  The all German  Registered Machinegun Receiver E guns are $50K and up.  Again depending upon the caliber, accessories and condition.   The German caliber conversion kits are in excess of $10K if you can find one.

IMHO, if you want the best and most up to date factory correct “HK21” than an HK21E built by one of the aforementioned builders using a latest generation M13 E parts kit with both 5.56 and 7.62 caliber conversion kits but be prepared to spend north of $60K for one.

If you want to use a transferable sear or box, than a German gun built off a HK91 using all German parts would be next in line but it’s going to be double (or more) the cost of a US built clone from MM or BPP.

I personally have a Michaels Machine 23EK / 21EK US parts gun as well as an all German HK21E/23E built off a G3 registered receiver and an M13 E parts kit (also built by MM) and am extremely happy with both guns.

As other posters have mentioned the HK belt feds are not the most robust and tolerant guns in the world.  The parts are extremely expensive and in the case of German parts extremely expensive and rare (a German 5.56 barrel can cost more than $5K by itself).  The star drive belt feed system is not the most robust and isn’t super tolerant in terms of dirt, links of varying pitch, rounds of varying length, etc. in comparison to guns with standard top cover shuttle arrangement like the M240, M60, or MG42.  Its also a sheetmetal gun built off a legacy assault weapons based frame vs. say a steel plate constructed gun like a M240 or 1919.  

The E guns are also extremely complicated to the point that many (if not most) owners are unable to take them fully apart or do basic part replacements, especially in the burst fire control group and the feed mechanisms.  I don’t know exactly how many individual parts comprise a complete 21E/23E system but it’s an enormous list of components and the number of people who can fully service these guns in the US (if you can’t do it yourself) is an extremely small list.

All that said, I love the 21E/23E system for what it is, its flexibility to convert calibers and from belt fed to mag fed, find the engineering and how they work pretty fascinating, and personally think they are one of the coolest looking belt feds out there.

Hope this helps and if you have any other specific questions I am happy to try and help answer them.

 

Edited by jbntex
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6 hours ago, johnsonlmg41 said:

 I would like to get a 23 conversion set but nobody seems to make parts that replicate German 23E parts for some reason?   R

Youre not looking, easily available.

Two options that are available BPP (beltfed precision) and MM (michaels machines) I would go with BPP as they are the closest to real German parts.  Gatewood supply has the barrels and you can call Carlos and get a feed mech/bolt/LP

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Posted (edited)

I have a 21, 23e (BPP), and 21a1 with german E parts, both 21 and 23. I prob shoot more than most HK owners.

23e BPP gets shot the most.

Most everything has been covered in preceding posts. If you want a HK type beltfed, just be prepared to spend a ton of money and break parts if you plan to actually use it. I would get a clone HK23e and get it set up with a sear. I recommend BPP over MM because his trunions are better and parts are closer to german. You will have to tinker with it to get it perfect, unless you buy a german parts built gun. 

I replaced most parts with real german parts in my clone gun.

I have shot out 5 barrels, broken 4 bolts (3 german, 1 clone/cracked in the corner where the rollers go), cracked welds, run through a ton of bolt locking lever springs and a couple recoil springs, broken 2-3 extractor pins (never broken a extractor).

pics for refence

23e clone it has about 80-90K but I stopped shooting it now that I have a 249,much better

JnvLJ58.jpg

latest gun, hk21a1 with german parts and heavily modded

MLalXNf.jpg

Edited by taylorwso

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Nice guns.   You don't see a 21A1 very often.

I would have thought you would have broken more stuff approaching 100K rounds.   I am not sure what the lifespan of an E gun is (either German or US) but figure 100K is probably getting to the top end service life of the receiver being welded bits on a sheet metal sub-structure.

I have not broken anything on either of my  MM or German guns but don't shoot them to that extent you do.  I put maybe 1000rds a year on the MM gun (maybe 8K or so in its lifespan  split between the two calibers) and even less on the German gun although put most of that limited mileage on MM bolts and barrels in the German full size E gun when shooting it as the German wear parts are very difficult and $$$ to replace.

KBqvbJk.jpg

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Posted (edited)

3 hours ago, taylorwso said:

Youre not looking, easily available.

Two options that are available BPP (beltfed precision) and MM (michaels machines) I would go with BPP as they are the closest to real German parts.  Gatewood supply has the barrels and you can call Carlos and get a feed mech/bolt/LP

I guess I will have to call. Nothing listed on BPP website other than "coming soon".  I did talk to MM a while back and they could not supply all the correct parts for my gun.  Maybe that's changed by now?  IIRC he did say the MM23 parts will not drop in, but wouldn't elaborate.

After all those rounds and bolt issues you didn't mention how many bags of extractor springs?  LOL

I'd say Jbntex is spot on.  I have a bunch tied up in mine, but that does put you into buying just about any beltfed you want so it does really come down to preference and interests.  Because of clone builders  there are more choices today than 10 years ago, and I expect more to come.

I'd still side on the MG42...old school all the way!!

IMG_8610.JPG

Edited by johnsonlmg41

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There are a couple mechanical differences between a factory German full auto E gun and either a US Clone E and/or a German built semi-auto E gun.

There are two major differences you have to keep in mind when trying to intermix parts between the two platform cousins.

1.  The barrel locking safety latch on a true E gun is different to the barrels are different.

The factory E guns have a little latch on the shroud that interfaces with a horizontal pin that sticks out of the barrel handle band.  When you rotate and lock the barrel in the little horizontal pin makes contact with the safety latch on the shroud, which rotates out of the way, and which then allows you to rotate and release the charging handle.   The US clone barrels don't have the little horizontal pin on the barrel band, so you can install a US Clone barrel but since it won't actuate the German E safety latch you can't close the charging handle and drop the bolt to charge the weapon.

The barrel safety mech on the US Clones (at least all the ones I have seen) is similar to the old 21s where there is a little pin that sticks out of the face of the barrel and interfaces with a hole in the face of the bolt.  On a US Clone if the barrel isn't rotated and locked that the pin the barrel will not index to the hole on the face of the bolt and will prevent the bolt from closing all the way.

If you put a German E barrel into a US Clone the gun will charge and may fire even if the bolt isnt locked into the trunnion.  Technically the E guns (both US and Clone) have extractors that protrude from the bolt face and go into the extractor slot on the barrel.  This also acts like a standoff (similar to the pin) but not much.  I have never tried to see if a US Clone with German unlocked barrel would fire or not.

To use a US Clone barrel in a German gun you have to add the little horizontal pin to the barrel.   Mike may have some pin he could add to one of his barrels (He did for me), if not they are really easy to make on a lathe and install yourself. You will also have to remove the pin that sticks out the face of the US Clone barrel by either pulling it out or milling it away.  If you don't remove the pin on the face of the US Clone barrel the bolt won't seat fully as the German E bolts don't have the index hole in the face of the bolt head like the US E bolts do.

2. The US guns are all built to use friction sears with the separate trip.    The bottom of the bolt carrier and bottom of the bolt head are different.  The German E carriers have a little spring loaded tail that interfaces with the one piece sear/trip in the factory German E guns.   On the semi-auto German E guns that I have seen set up for a sear, the builders will remove the spring loaded tail from the carrier and weld on a ramp to trip the friction sear.  The US Clone and the modded German Semi-Auto E bolt heads also have to have a channel milled down the bottom for clearance of the sear trip as the bolt actuates back and forth.

You can put a US Clone bolt head in a factory German E gun (semi or full auto) as the trip clearance slot doesn't matter.   However you can't put a German E bolt head into a US Clone or a Semi-Auto German E with a conversion sear unless you mill the bolt head for clearance.   You can put an unmodified German E bolt head into a German E semi without a sear as there is no sear trip in the way.

You can't put a factory German E carrier into a US clone or a German E semi with a sear as it won't trip the friction sear.  The same goes in reverse as you can't put a US Clone carrier in a factory full auto German E gun as the carrier won't trip the one piece sear.  You should be able to put a US clone carrier in a semi-auto German E gun with a sear and be fine as that German Semi E is mechanically similar to a US Clone from a sear trip perspective.

You would need to sort out with MM or BPP how your German semi E with a sear is set up from a barrel locking latch perspective and sear trip in order to get the right US parts to function.

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jbntex,

yep knew about the barrel mods.  Had some FMP barrels done a few years back with the pin mods .....and the expensive plastic handles.   I know there are some carrier mods etc. but I only have the one gun these days and no clone guns to compare to, so I threw in a pic.  I do have at least a couple more new bolt heads, but haven't looked at them for a while, they may be different but are supposedly 21E from what I recall.  Thanks for the insight!

IMG_8613.JPG

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Posted (edited)

Your bolt carrier looks to be a  German E 7.62x51 Carrier with with a welded on trip to replace the tail although its hard to 100% see how the trip is done in your picture.  Can you post another pic of the sear trip/ramp area.

However, it doesnt look like your unit had the clearance slot milled so the sear trip appears to be dragging on the bottom of the carrier group.  On yours you can see the line the whole length along  the bottom of the carrier that is in alignment with the welded on ramp where the sear trip is rubbing the bottom during the recoil stroke.  Over time I assume the sear trip  will get beat up as tip of the trip gets pushed  into and back out of the gap between the bolt head and carrier on each firing sequence.

Here is a German 23E vs. MM Clone BCG.  You can see the trip difference and the relief slot for the sear trip.

Assuming you have the barrel latch/pin sorted out you should be able to use a MM23E US BGC in your semi auto E gun.

The feed mechs at least on the MM unit I have is a mechanical functional mirror of the German 23E feed mech as far as I can tell, although there are some slight finish and machining differences between the US and German units.

Hope this helps.  I would give MM or BPP a call as those two guy probably know more about the platform than I ever will....but their parts should work in your German E semi with sear gun.

 

s1MUDCs.jpg?1

Edited by jbntex

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Fellas! I know Sturm has some institutional knowledge but I’m floored with all the info in response to my question. This is exactly the kind of feedback I needed. I’ve just completed a first pass but will need to take some time to digest it all. 
 

Thanks so much for all of the detailed responses. 
 

Chris

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I have to say I have learned a good bit on this thread too. I wasn’t sure what parts would swap around between HK and host manufactures...other than I knew the BPP guns don’t have the alignment pin clearance for barrels. 

Youre correct-this site is great for gathering information like this. 

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18 hours ago, johnsonlmg41 said:

After all those rounds and bolt issues you didn't mention how many bags of extractor springs?  LO

I think Ive used one in the 23e, the way the extractor is set up it doesn't put any pressure on the spring.  Now on a 21 yes a few

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Posted (edited)

I took a look this morning and I'm not sure the MM or BPP parts will work?  I would need another German carrier for sure.  I don't know if the carriers are the same for 21E and 23E guns?  This gun has all German parts except for the sear.  The drag marks on the bottom of the carrier are from a modified 21E sear trip, not from the typical friction lever setup like on the rest of my HK hosts, so this whole thing works as a package utilizing the pivoting lever on the bottom of the carrier and not needing a ramp in this case.  This carrier is tungsten filled.   To sum up what I'd need:

A German 23E carrier with bolt

23E barrel with the bigger side pin (not the end of barrel pin)

Feed mech

Is the recoil spring the same, or different compression?

A few years back when I posed the question I think 7-8K was the answer for the parts?  At that point I'd be cheaper buying a complete 23 clone?  Maybe the prices have come down?  LOL

 

 

IMG_8614.JPG

Edited by johnsonlmg41

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18 hours ago, jbntex said:

Nice guns.   You don't see a 21A1 very often.

I would have thought you would have broken more stuff approaching 100K rounds. 

I swapped out the clone parts (when I first got the gun) for german, that's why. Feed mech is the only thing that hasnt break- well its missing the cartridge stop but It runs fine w/o it.

I did have to have it re-welded, there was a crack forming where the end of the trunion was, suspect the metal was bent/stretched causing a stress that became a crack.  One weld was done w/o filler and it cracked.  The trunion is still perfect. 

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Posted (edited)

1 hour ago, johnsonlmg41 said:

 

That is interesting I have never seen a conversion sear used in a 21E/23E host with a factory E bolt carrier before.   

So the builder modified a factory E sear into some sort of E "trip" for a friction conversion sear?  Can you post a picture of the pack, I am really curious how they turned a factory E sear into a friction sear trip. 

So in your case it looks like you would need:

1. Clone 23E Barrel, remove the bolt face pin, add the horizontal barrel band pin to engage the E safety mech.

2. A US Clone 23E clone feed mech  (the MM and German ones are interchangeable in my experience)

3. A German 23E carrier.

4. A US Clone Bolt Head. 

5. A German or US Clone 23E locking 20T piece.

In my all German Registered Receiver  gun I run this exact setup from a barrel and carrier/bolt head combo.   

This puts the wear and tear on a US Clone Barrel (keeping my German 23E barrel unfired) and also lets me run a bolt head with full round rollers vs. the half moon rollers as well as keep my factory 23E bolt head unfired.  (HKParts has German 23E carriers, which is where I got my spare one to run with the MM bolt head)

I primarily run the German E feed mech on my German RR gun since I am not concerned about wearing it out but have installed my US MM23E feed mech on it as well.

I use the same recoil rod/spring for both 7.62 and 5.56 setups.  I have gotten conflicting information over the years that the 7.62 and 5.56 guns use the same recoil spring or different recoil springs.  RTG parts lists two different springs for the 21E and 23E, HKParts lists just one combo spring, and when I talked to Mike he said you use the same spring for both. He built the guns, so I just follow his advice and use the same spring in both.

I think it would run you $1500 for the US barrel, $800 for the carrier, $500 for the US bolt head, $200 for the LP, $4000 for the US Feed Mech.  

Figure all in ~$6000 to $6500ish.

The last pricetag I heard for a complete MM23E gun was in the $13K to $15K depending upon options, how you pay, etc. so the conversion kit above would be much cheaper route vs. a whole gun.

 

Edited by jbntex

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After taking it apart and reviewing it again compared with a new spare 21E (unconverted new factory) trigger group, the sear catch mechanism is completely different than the new one.  On the new group the sear leg comes up as one piece and is tripped directly by the carrier.  Because this a  Fleming reg. sear, there is no extended leg, but it is tripped by a sliding (vs. pivoting on friction conversion sear groups) sear catch that moves the friction sear.  I'm guessing this is early E stuff, not available today (course not much is any longer) that had slight mods to make it work vs. a complete redesign closer to all the other standard products.  I was told the gun was somewhat unique and have never been able to verify the builder. 

Firing pins, springs, rollers, belt box, spare barrel, barrel cases, shipping, etc. and we're pushing 10k.  Hard to justify for me, course it's HK stuff and logic has no application there.  Dang, hate that "on the fence feeling"!  Probably could use some peer pressure?  Why does buying HK stuff always seem to feel like you dropped the soap in jail?

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Posted (edited)

4 hours ago, johnsonlmg41 said:

 I don't know if the carriers are the same for 21E and 23E guns? 

They are not the same, the 21 has the cam channel about 6 thou farther "out" You "might" be able to use a 23 with a 21 feed mech as its been done but you could have problems. 

 

And the springs are different,  couple extra coils, but I've interchanged both.

eno2idC.jpg

eno2idC.jpg

Edited by taylorwso

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Interesting measurement on the 21A1 carrier.  Does the 21A1 advance the belt on both recoil and closure stroke like the E or is it like the older 21s where it just advances on closure?

Seems like there is a lot more slide camming action on the feed mech slide on the 21A1 carrier.

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OP  $$$ will decide what you buy. I have a MM21e/23e with one of my Flemings sears installed into a four position lower, that I've had for 8+ years now and have run about 9k of each cal. and I have three bbl's for each cal. I have only broken one extractor. I have shot both cals. suppressed with 100% success. Anytime I call Mike regarding ordering an extra something or just a general question, he always answers the phone.

 

YMMV

 

Good Luck

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On 8/29/2021 at 1:48 PM, jbntex said:

Interesting measurement on the 21A1 carrier.  Does the 21A1 advance the belt on both recoil and closure stroke like the E or is it like the older 21s where it just advances on closure?

Seems like there is a lot more slide camming action on the feed mech slide on the 21A1 carrier.

older 21

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Not to pile on but these responses were incredible and so helpful. I'm grateful for all of you who took so much time to capture and share your learnings.  Thanks!

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