Heckler & Koch's Modular Machine Gun: the HK21E

hey guys thanks for tuning in to another video on forgottenweapons.com i'm ian mccollum and i'm here today at morphe's taking a look at an hk21e this is the fully modernized version of hk's light machine gun based on their sort of universally applied roller delayed blowback system so this dates to the early 1960s uh of course at that point hk had gotten a contract to manufacture g3 rifles for the german military and they got part way through that contract and decided you know what we need to have like a companion light machine gun or squad automatic weapon to go along with our rifle they were looking at selling these things the right the g3 rifles as well as what would become hk21s uh widely on the international market and it makes sense that if you're going to make a rifle you make a light machine gun to pair with it this is something common we'll see it with the fn fal where they had a heavy barreled squad automatic version of the foul colt had a number of developments for light machine guns the cmg-2 and cmg3 that it tried to market alongside its ar-15 m16 rifles and hk had the same idea now hk would be very successful in scaling their roller delayed mechanical system both up and down so scaled down to nine millimeter you get the mp5 submachine gun and all of its variations you have the g3 rifle as well as the hk33 in 556 and all of those variations in length and such and then scaled up with a heavier duty receiver a heavier barrel a quick change barrel and a belt feed mechanism and you get the hk-21 i've discussed hk nomenclature a bit in the past suffice to say at this point the first digit tells you what type of firearm it is so uh in this case 91 indicates a shoulder rifle uh 21 indicates a light machine gun a met a belt fed light machine gun worth pointing out hk 11 the numeral 1 is the first digit indicates a magazine fed automatic rifle so and then the second digit describes the caliber so in this case 21 2 means a belt fed light machine gun the one digit indicates that it is 762 nato caliber uh last digit being three indicates five five six so uh hk would develop the hk 23 as well which is basically the same gun here in five five six anyway i'm getting ahead of myself 1961 they come out with the hk21 and at that point is very much just a g3 receiver kind of modified to have a quick change heavy barrel and a belt feed mechanism and the first major contract for the user the first major buyer is portugal portugal has adopted the g3 as its standard rifle and they go ahead and adopt the 21 as a standard light machine gun they designated the m968 in 1968. the german military would never adopt these large scale because they already had a universal machine gun they were very happy with that being the mg3 an updated version of the mg-42 this was more for smaller countries second-tier military forces who were going to be ordering things not from their own domestic arms manufacturers or state-owned arsenals but from export companies like h k so in the 1970s they would go through and make some updates to this that resulted in the hk21a1 the us actually tested this in 1974 but opted not to adopt it and then in the early 1980s would come the hk21e the e is for export model and it includes the improvements and strengthening of basically all the components so everything from the recoil buffer in the buttstock being improved the receiver was actually lengthened about an inch to allow greater a longer bolt travel which reduces felt recoil the barrel shroud at the front was extended a couple inches that gives you a longer sight radius the barrel was made a little bit longer the bipod was improved the attachment mechanism for the belt feed system was improved the belt feed itself was improved they added an up an option or a mechanism for attaching a belt box to the gun the barrel removal handle was enlarged the fire control group went from uh sem safe semi full to safe semi three round burst full for those who wanted it at least they added a forward assist to the receiver they like the whole gun got overhauled it actually gained about three pounds in weight in this process uh the original hk 21s were 7.9 kilograms which is about 17 and a half pounds the 21e version uh has inflated that to like 9.35 kilograms which is 20 and a half pounds so picked up a couple pounds along the way one of the elements that really sets the hk21 apart from a lot of the other light machine guns out there is its modularity and this is in particular true with the 21e version it can actually be readily swapped between 308 and 556 calibers it can be swapped between a number of different barrel lengths that's not difficult and it can also actually go to magazine feed very easily so let me show you how well that actually works one of the design elements that came about with belt fed machine guns was the top cover the idea that you have a pinned piece uh piece pinned at the front that will open up and allow the shooter access to all of the internals of the gun from above where they're easy to look at easy to manipulate easy to fix if anything breaks and this has been kind of standard for belt fed guns for nearly 100 years now however if you're going to take an existing platform like the stamped sheet metal receiver of a g3 rifle and make a belt fed version of it you can't really do that adding a top cover to an hk roller delayed gun would completely change the receiver in for the receiver architecture so instead they put the belt feed mechanism on the bottom here and in true hk style it is actually modular and detachable so before i take it off actually i will show you there is a latch here which allows you to drop the bottom half of the feed mechanism you do that for loading and for safing the gun having this open ensures that there is not a round in the feed way now these are closed bolt firing guns just like all of the other uh hk uh fam hk roller delay family of firearms so that has some pros and some cons when it comes to a light machine gun the benefit is it tends to be a very accurate gun in semi-automatic fire because the bolts already closed when you pull the trigger the barrel is fixed because it's not a recoil operated gun so semi-auto very effective however in trade-off uh you have less cooling ability than a traditional open bolt gun because you don't get air circulation through if you fire enough to heat up the barrel to the temperature that around can cook off well a closed bolt firing gun is always going to come to rest with a cartridge sitting in the chamber waiting to fire so on an open bolt gun no matter how hot the barrel gets you'll never have a cook-off because rounds aren't sitting in the chamber with a closed bolt gun they are and so a cook-off is a potential hazard it's just an issue that you have to be aware of with a gun like this now you may have noticed that the bottom of the belt feed module here is open and exposed to the elements and the reason for that is that there is a belt feed box that sits on top of it here and closes that off there we go so with the box in place you no longer have all that dirt or mud exposure the box here by the way has this kind of cool system where there's a little spring clip here that keeps the box closed you've got just enough space for a starter tab of the belt and when you want to use it you lift this catch up and then this will open just enough like that to let the belt come out without opening a huge gap in the box to remove the belt box because it is it does latch in place you have a button here or a lever here allows you to take it off now the left side of the barrel shroud is solid with vent holes here for airflow we have our charging handle which functions the exact same way as on a g3 rifle it's just a little bit bigger to give you a better grasp on it i'm going to go ahead and lock this open like so now you have to have the bolt open locked open to change the barrel because the extractor actually sits in a little cutout in the breech face so once once you've got the bolt locked open you can push this in rotate the barrel up just slightly and then it slides forward and using this big plastic handle you can grab it and pull it out of the gun replacing the new barrel is just as easy i have here an hk 11 length barrel slide it in comes in there and just snaps down and locks into place and the barrel's changed and ready to go a nice detachable bipod on the front this mounting system gives you a nice amount of pivot or does when the bipod's not folded up kind of inspired by the mg34 mg-42 system so the legs just snap out in order to retract them you have to push the button in and then snap the leg back these legs are fairly simple they're not adjustable for length they're not adjustable for any angle other than locked in the straight open position and then you get a fair amount of pivot on the gun as well as a little bit of play here but you can push solid or pull solidly into the bipod now the modularity of the gun really comes into play when you want to change calibers or feed systems so of course you saw how you can change the barrel out there is a single pin right here that locks the whole feed assembly in place so i can pull that entirely off uh they do have feed blocks uh belt fed feed blocks in 556 caliber this is in 762 nato but the two are completely interchangeable their external dimensions are the same even though the cartridges are different in length what we can do here should you want to is replace that belt feed mechanism with a magazine feed tower as far as the gun's concerned no big deal it doesn't really care cartridges present here and feed out of magazines just fine so we can use that same pin lock this there we go lock that in place there there's a little spring catch right here that holds this up in position and then you can use standard 20 round box magazines in the gun now originally when hk designed the hk 11 which was the used this shortish barrel length and was specifically intended for box magazines they actually developed a double drum magazine but the hk 11 was never a particularly successful gun not like the 21 and 23 and so those drum magazines were dropped from production and are really quite scarce a couple other items to take a quick look at here there is a forward assist on the receiver this was added as part of the 21e upgrade program you can see the ratchet cuts here on the bolt that is more for allowing you to drop the bolt quietly not such a big deal on the ar pattern but hk requires the bolt to be going fairly fast to actually lock those rollers into battery at the end of travel and if you want to do that quietly well that's difficult unless you have a little manual lever that you can use to force the gun force the bolt into battery after letting it down gently so that's there there are scope mounting blocks here that's part of the 21e upgrade as well the drum site is not used on the 21 instead it has a single rear aperture sight and a big ol elevation drum that allows you to crank it out to 1100 meters or all the way down to 100. the stock has this clubfoot design that you would expect for a light machine gun the original hk21s in the 60s did not they used a standard g3 stock this was another one of the improvements actually an improvement from the 21a pattern in the 70s that carried over to the 21e notice also we have a pair of little trunnions back here that are for mounting the gun on a pintle or tripod mount the front part of that system is this lug right here so this can be used as a vehicular gun as a sustained fire tripod mounted gun again part of the the modularity of the system and before we wrap this up i will go ahead and show you the internals so disassembly is just like a any other rifle in the family pull the pins out and store them there in the butt stock once i pull the stock off we of course have a recoil buffer in the stock that was something that was strengthened and improved for the 21e and we can then pull the bolt carrier assembly out the back of the gun so there's our captive recoil spring and there's our bolt carrier if you're familiar with the g3 rifle there's really no surprise here um the one difference is there is a track on the bottom of the bolt carrier that acts as part of the feed system for the belt feed unit so that this will this will cause the belt feed unit to actually cycle as the bolt goes back and forth it pulls rounds up on the belt so these parts are not interchangeable with the g3 in fact basically none of the components except maybe some small things like pins are actually interchangeable with the g3 the mechanical system is the same and the parts are modular within the hk21e family itself but not with the rifles the advantage to having this system if you use g3 rifles is that your operation and training is uh protocols are basically the same across the whole platform troops who are familiar with the g3 rifle will be fairly familiar with the hk21 pretty easily i do also want to show you the fire control group note that it does not have a pin in the front this is a an hk21 standalone fire control unit again where a lot of the other a lot of the rest of the roller delayed family is interchangeable the fire control unit here is not one of the other changes that was made with the 21e was the addition of a burst setting in addition to full full auto so that's uh that's what you got there you can see the receiver here with its reinforcing up here as well as back there and that's about it all right there you go there is an hk21e field stripped out with both belt and magazine assemblies basically this is a 21e and also an hk11 e the hk21 would prove to be a fairly successful commercial venture for hk by 1977 they'd sold some 20 000 of them across 20 different countries that's nothing to sneeze at they had a number of countries that purchased licensing rights to manufacture the gun domestically those would include portugal and mexico and maybe another not entirely sure the gun today has been replaced in hk's you know catalog lineup by the mg4 and mg5 in 556 and 762 respectively but there's still a lot of popularity for the old stamped steel roller delayed system just as we see in submachine guns where they can't seem to stop selling mp5s despite having the ump available so uh these certainly have a lot of cachet here in the us people think they're extremely cool guns because frankly they are extremely cool guns i have a shooting video that i did on one of these that i'll link at the end of this video so if you're interested you can check that out that was done uh courtesy of hk and trijicon so thanks to them and of course thanks to morphes for giving me access to this particular one with its whole smorgasbord of accessories and adapter parts to show to you hopefully you enjoyed the video thanks for watching

Channel: Forgotten Weapons

Views: 478,186

Keywords: history, development, mccollum, forgotten weapons, design, disassembly, hk, heckler, koch, h&k, machine gun, omg, light machine gun, hk21, hk21e, hk11, hk23, belt fed, magazine fed, export, greece, Mexico, portugal, m968, modular, interchangeable, 556, 308, 762, mg3, minimi, g3, rifle, roller delay, German, germany

Id: kZWtGiESQ4s

Length: 17min 58sec (1078 seconds)

Published: Mon Oct 26 2020

Reddit Comments

[u/teamdankmemesupreme]

At the risk of sounding stupid, what is the thing hanging from the barrel on the right side? And left too