Four Fun Facts about the Oerlikon 20mm Antiaircraft Cannon!


Hi guys, thanks for tuning in to another video on forgottenweapons.com, I’m Ian Mccollum. and I’m here today at the rock island auction house because they have this monstrous 20mm full auto anti-aircraft cannon they’re going to be selling it in their may of 2017 auction and I thought it would be cool to take a look at a few fun facts about the mark 4 mod 1 Oerlikon cannon. Interesting fact #1 would be that these guns were used by both sides in world war 2 Probably more extensive by the United States navy by anyone else but the germans, the americans, the british and the japanese and the italians all had Oerlikon Cannons. In fact, between December 1941 and September 1944 these guns were responsible for 32% of all japanese aircraft shot down by the United States. That is quite a substantial percentage. Interesting fact #2 is that these are actually open bolt guns. Meaning there is no locked breach, despite this being a massive 20mm cartridge. The way this works is actually what is called advanced primer ignition. Now, this is different than what most people think of on submachine guns On those, you’ll have a fixed firing pin that will fire a cartridge immediately upon chambering it. Well, the chamber on this gun is a bit different. It’s an extended, long chamber that’s actually longer than the cartridge is. and the cartridge has a rebated rim so that the entire bolt head fits inside this long chamber. So the cartridge is fully supported, sliding forward, into the last bit of the chamber and still moving when the firing pin protrudes forward, fires the cartridge. The recoil energy then has to counteract the forward movement of the bolt, and then start pushing it backwards. That reduces the felt recoil and makes this a much simpler gun to mount and use. Now, the downside of that arrangement is that its got a really heavy recoil spring in it. Because that is the only thing holding this gun closed. And I’m not kidding when I say really heavy. With the round recoil spring wire, like we have in this gun now, When it is fully locked back, the recoil spring is exerting 396 pounds of force forward on the bolt. and that begs the question, how are you supposed to cock this thing? The bolt right now is all the way forward, so how do you get it back? Its the equivalent of having to dead lift 396 pounds against the gun in order to cock it. So the bolt is connected to these action arms, one on each side of the assembly which then come up to this sleeve which retains the front of this huge recoil spring and in order to cock it, this whole thing has to go backwards. Let’s see if I can get it started. Aaargh, all right, I can get it to move a little bit, but that’s not going to work. Helpfully, they put this little tiny cocking handle on the back of the recoil mechanism. So, what do you do? You take your cocking rope and you hook it onto that hook, You then elevate the gun all the way up to vertical, And then the world war 2 pedestal mounts had a little pully, right here. So you take your rope from this hook, around the pully, and then hook it to the base of the mounting pedestal. Once it’s in place, then you have the leverage from the shoulder rests, pull the gun back to horizontal, That is going to pull your charging handle all the way back and cock the gun. In case that didn’t work, you did have two other options. One was a big old block and tackle system that you could pull out of a crate somewhere and bolt to the side of the gun. And use that to pull the charging handle back by hand without the extra leverage of the mount. The other was actually a ratchet system that you could bolt onto the back of the gun and use a geared ratchet to slowly pull this back with a big lever. Fun fact #3, these were primarily naval guns, which meant they had muzzle covers. But If you’re out at sea and its below freezing and there’s spray coming over the gun You’re going to get ice on the gun. Well what happens when you get ice on the muzzle cover and it freezes to the barrel and you can’t take it off? You’re firing high explosive projectiles so you probably don’t want one of those hitting a big block of ice at the end of the gun. I think that would be bad. More to the point, what if some sailor just forgets to take the muzzle cover off and fires a high explosive round right through it. That stands a pretty decent chance of detonating on the muzzle cover, and that’s a really bad day. Well, they did think about that, and the answer lies in loading the drum. This, by the way, is a 31 pound, empty, drum when full it holds sixty rounds And, the way you’re officially supposed to load this gun is 58 rounds of high explosive in the drum and the last two rounds you load, to top it up to sixty, are both inert bullets. So no high explosive, just a solid projectile. And, according to the manual that will allow you to shoot through, safely, up to 1 inch of ice holding the muzzle cover on. Or, if you just happen to be an idiot, firing through the muzzle cover that you forgot to take off. Two rounds will make sure to clear the muzzle cover enough that you don’t have to worry about blowing yourself up with the next HE round in the drum. Fun fact #4. What is the official navy position on mag dumps from the 20mm Oerlikon gun? Well, the answer is that you could drop five magazines through this as fast as you can and not really do any damage to the barrel. At nine magazines, however, dumped as quickly as you can, You would seriously damage the barrel. So, it’s recommended that you lay off a little bit in between drums. Or, alternatively, change out the barrels. One of the advantages of the Oerlikon gun is that you can actually change the barrel out in about 30 seconds. The other alternatives out there like the hispano suiza required a significant teardown to replace the barrel. Oerlikon, not so much. Grab your spare barrel, throw it in, nice cold barrel and you’re good to go. Alternatively, according to the manual, if you don’t have the spare barrel handy Or you can’t change it, dump water on the gun and keep the barrel cool that way. Well if you happen to have a patrol torpedo boat that is in need of some new armament or perhaps, way too much free space in your living room… and you need something to fill it, take a look at the description text below You’ll find the link there to rock island’s catalog page on this particular gun It is, of course, an NFA registered machine gun But that won’t stop anyone that can pass the background check from puchasing it. So, take a look there. Ah, you can place a bid online, although for something like this you probably want to come down and and participate in the auction live. Thanks for watching!

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Comments

  1. Just informed the missus that I'm off to auction to buy a 20mm anti-aircraft gun.
    She informed me that if I go to auction again, she goes for good…
    On the bright side, at least now I have enough space in the living room for my new Oerlikon!

  2. Wonder if it can fire nerf rounds , just the thing for the kids parties . Hey you off the fence "whoommfth , whoommfth " , eeer MEDIC !

  3. Or if u just happen to be an idiot or u just happen to be being chased by airplanes. That will tend to make u forget simple things such as a muzzle cover

  4. And in the event al those chaging systems fail you get a burly guy from the main gun ammo handling area to come around and charge all ur Oerlikons….cuz im sure they get buff humpin those big ass shells all day.

  5. Fifth fun fact….Clark Gable fired this from the back of his Chinese junk ship in the 1955 movie, "Soldier of Fortune"…always loved that gun. See here timeline 1 minute 59 to 2 min 05….
    https://www.youtube.com/watch?v=Ye_XCOoAdxU …. and here from 2, 28 to 2,35—>
    https://www.youtube.com/watch?v=LIbX54doYmo

  6. I wish my father were still alive to watch this video with me, this was his primary weapon in the US Navy Armed Guard in WWII.

  7. “Oh dear lord, Please of reminded the guy loading these mags to have the last 2 inert”!!!!! “I promise I’ll never drink again “!!!! haha 😂

  8. Shriek! They shouldn't be able to sell a 20mm fully semiautomatic autocannon assault rifle! Just because it isn't painted scary black doesn't mean I don't know what it is. Take it away! Somebody may put a 30-round clip on it, and shoot up a movie theater full of anti-gun people watching a Hollywood movie full of, uh, well, "gun violence." Oh the humanity! Take away everybody's anti-aircraft guns. Even the ones made in peaceful socialist Sweden.

  9. Are these guns capable of firing from a slightly submerged position? I'm a little sceptical of a war story I was told by my pa.

  10. It was air to air, but a gun to look at would be the MK108, a 30mm cannon the Germans used in the latter part of WW2 to combat enemy four-engine bombers, as 20mm cannons were thought to lack punch against heavies.

  11. Thanks for the video. As a swiss I would have liked to hear a bit more of the development and origin of this AA gun ;-). BTW I served using its successor, the ”20mm Flab Kan 54” from the same manufacturer, which was introduced 1954 in the swiss army. Much more powerful and accurate thanks to a longer barrel and a muzzle break.

  12. What fun by an auto canon… Build your own technical! Defend your land from FBI take overs, discount to American Aboriginal land holders offered! SHOOT down a zero or Me109… Near new condition. Need friends to cock.

    Sexy gun. I WONDER if its good for dispatching unwanted uncles in the Nth Korean vein

  13. As a former RN Gunner it was my fav weapon. I had misfire. We waited 20 mins, took mag off and saw the round had been struck. Sub Lt wanted to shove broom handle down to poke out the round. Skipper said "belay that order" and over the side went the barrel

  14. I'll stick to my pigeon grade Winchester 20 gauge.
    We used rockets to shoot down Iranians aircraft, curticity United technologies and Raytheon.

  15. Oh my god I wish I pick that up. I’d love to replace my piano with a really anti aircraft gun. I’d steam punk the shit out of it and just put it in my living room.

  16. For users of the metric system:
    Why do you still use millimeters for measurements beyond a centimeter?
    Why not call it a 2 cm? Serious question

  17. More like a dumbbell row than a deadlift. Cool video as always though! Edit: NVM, I didn't know about the rope, hook and pully.

  18. Love 20mm Cannons…I loved my Oerlikon 20mm GAMBO in the Royal Navy. The 30mm was good but a bastard to reload…20mm was excellent it felt refined and yeah it was a derivation of Gun-Jesus-Ian's one above it was epic 200 rounds of Hate going down range. Drone shoots are fun. http://www.seaforces.org/wpnsys/SURFACE/Oerlikon-20mm-gun-UK_DAT/Oerlikon-20mm-gun-05.jpg

  19. The joy of being a neutral country is that you can sell to all comers, Switzerland in the case of the Oerlikon. Sweden, which positively revels in its neutrality, peddled Bofors guns like candy to every Tom, Dick and Harry. Being peace loving neutrals, they never SOLD the guns to anyone. They simply licensed the manufacturing rights to others. BTW, Bofors guns were jointly developed by Sweden and (gasp!) Krupps

  20. He forgot to mention that cartridge cases for this gun are lightly greased before loading.Not something you would dare do on small arms ammo,and most artillery fixed and semi fixed ammo.

  21. wooow! i really like this version of your videos… fun facts is shorter and even more interesting than video describing full tech..!!! Ok those videos is also neccesary

  22. I can see the interaction now:
    Game Warden, "Whoa, there, son, I need to check your license and gear… Um … Let's see …. Hunting license, check. Land use permission, check … Weapon … Uh … Son?"
    Local Dude: "Yes, sir?"
    Game Warden: "You … um … you got the required center fire, mushrooming ammunition in that thing?"
    Local Dude: "Sure, sure, 'mushrooming' yep."
    Game Warden: "Ummm … oooookay … I'm just gonna go play in the next county for the afternoon. Y'all have fun now."

  23. My father used that type 20 mm cannon in WW2 on board a Wickes class destroyer coverted to fast minsweeper. He was a gunner's mate 2nd class. Funny thing about his gun position. It was not official. The ship would add 20mm and 50 cal guns to their ship for added fire power during convoy escort and minsweeping duties. If they had to come state side all the extra guns were dumped over board before state side inspection. Or at least that is how I understood it. The system you have shown does not seem to have sights on it.

  24. This is the gun that the Swiss wanted Charlie Wilson to arm the Afghans with to fight the Russians…

    They tried to convince him that it was mule portable…

  25. One of the characters in Thunderbolt and Lightfoot even though it was not a tank weapon that's they said they used for

  26. I am in shock over the procedure to cock the weapon. In the heat of battle if you have a misfire, that would mean the bolt traveled all the way forward and needs to be re cocked to get the misfired shell out and to chamber a new round. Hate to be the guy dicking around with a rope during the melee

  27. This is a must buy. I have one mounted to the roof of my home and not a day goes by that I don't use it. It's true, I'm not very fond of my neighbors, their pets, any vehicle or aircraft, but that's kind of on me. Since the live rounds can get expensive, I usually save those for use on the unsuspecting local fauna. People get upset because they say I'm shredding all of the trees.

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