M20 75mm Recoilless Rifle: When the Bazooka Just Won't Cut It

hey guys thanks for tuning in to another video on Forgotten weapons comm I'm Ian McCallum and I'm here today at the James Giulia auction house taking a look at some of the tank weapons that they are going to be selling in their upcoming spring of 2018 firearms auction and this is an EM 20 recoilless rifle and despite the look this was actually developed and introduced just at the end of World War two now the issue that this was developed to address was that of rapidly increasing tank armor so we all know that during World War two you know at the very beginning tanks had really quite remarkably light armor such that in fact most countries had some sort of man-portable approximately 50 caliber anti-tank rifle that could be used to effectively incapacitate light tanks or really the tanks that were in use and by the end of the war you've got things like German Tiger two's that are impenetrable to virtually everything so the u.s. first off didn't have an anti-tank rifle at the beginning of the war and kind of had to play catch-up developed a bazooka the 2.3 6-inch bazooka which was okay but quickly became not powerful enough so they replaced that with the super bazooka which was a three and a half inch bazooka that was better but still not powerful enough for a lot of the armor that was coming out so u.s. ordnance began to experiment with the concept of a recoilless rifle the idea here is you have a gigantic cartridge and it's perforated in the case body and there are vent holes in the back of the breech and so the see the problem is if you were to fire this out of a typical sealed breech rifle sort of gun the recoil would be absolutely tremendous because all of the pressure that builds up to fire in this case a 75 millimeter 22 pound a 10 kilo projectile all that energy is going to be transmitted into recoil in the gun so one of the alternatives what they call a recoilless is to not try to contain that pressure at all and what you're basically doing this is kind of like a rocket except it just gets one big burst of propellant gas so when the powder charge in this detonates it explodes here and then it has two places that it can go one is forward but it has to move the projectile in order to do that one is backward well simply because it can't all escape out the back at once half of that pressure gets transmitted into the projectile and it goes flying out the muzzle the rest of it vents out the back of the gun as a result you don't have to try and make the back end of this thing strong enough to actually contain all of that pressure while the projectile is going up the barrel that allows you to make the weapon a whole lot lighter and more portable so instead of having something that you know requires a five man crew and has a big wheeled carriage and has to have a truck to tow it as you would get with a 75 millimeter artillery piece instead you get something that weighs in total with its mount 114 and a half pounds 52 kilos something that can actually be more or less transported by a team of two or three men on foot now when the u.s. started working on this they actually worked on a variety of different calibers and in fact the first one was a 57-millimeter gun that was actually shoulder-fired that developed well and actually went into production as the m18 and did see use at the very end of World War two starting in about March of 45 and when they were developing that gun the Ordnance Department looking at it and said this looks pretty good we should develop it in several other calibers as well and so in addition to 57-millimeter they developed versions in 75 millimeter and 105 millimeter this being the 75 was adopted as the m20 and went into service right about the same time March of 1945 so these saw just a little bit of use right at the end of World War two they then saw substantial use in the Korean War and they were kind of just on their way out in the Vietnam War being replaced by guided missiles basically wire-guided missiles so this fired a 75 millimeter or three-inch projectile weighing about 22 pounds had a couple different types of ammunition they had armor peers that had high explosive they had higher explosive armor piercing and they had a white phosphorous round which was used to create smoke clouds and with the armor-piercing round they could penetrate it was a shaped charge so it didn't really depend on velocity but they could penetrate about four inches of armor which even for something this size wasn't really otally capable of taking out a Soviet t-34 which was one of the main enemy tanks in use in the Korean War so still not a totally capable anti-tank weapon in Korea although it was pretty darn good at the end of World War two the effective range of this was about 400 yards in theory the maximum range is like seven thousand but effective range for a point target was about four hundred maybe a thousand yards with the high explosive ammunition speaking of which unfortunately I don't have the optics here to show you but this actually has a mount for two different optics it had a direct fire optic for basically shooting at tanks and it had an indirect fire optic which would have been used for the high-explosive rounds the indirect fire optic allowing you to angle the gun up substantially an aim at a target where you're dropping around down onto your target the mount for this what we have here you know rather clever maybe obvious but clever decision was to use the mount for a model of 1917 a one machine gun the u.s. still had plenty of those around in World War two and it makes a nice convenient mount so the pintle is identical to the pintle for a 1917 machine gun this just drops in and that's a nice easy solution without having to develop a whole new mount you'll notice it's actually pointing 180 degrees the opposite direction that a machine gun would if you had a 1917 machine gun on this be pointing that way this allows you to angle it up reasonably substantially with this long barrel on it and that was the the primary ground mount these were also mounted on vehicles jeeps primarily 105 millimeter ones were too big for a machine gun mount they were primarily on vehicles as well as having I believe a wheeled carriage let me go ahead and show you a bit of a close-up on the breech mechanism how that works and a few other details all right so the way you would go about actually firing this is well first we have our breech block back here and you can see the four very large vent holes where all the propellant gas comes out the back so you would take your projectile here now this is obviously just an empty case and just FYI the projectile on this thing comes out to like here it's almost as long as the case itself it's huge so you take this and you rotate it about 45 degrees and then it pivots open like that we have a firing pin hole down here and a little cartridge extractor you then take your case slide it gently into the chamber there this one's got a bunch of preservative grease inside so I'm not going to try and chamber an old empty cartridge anyway once you've got that in you then close the breech block and by the way you don't do it like this what you would do is actually be able to see this you would get back here so that you are not behind the action close it rotate to lock that's a very important part you know I can't really overemphasize just how dangerous the back end of these things is remember literally as much blast comes out here as comes out the front end so once it's locked in in position then we've got our trigger mechanism the trigger for this is right here on the left hand breech handle so we have a button there there is a safety device to it you can rotate this that safe that's ready to fire your that click that is the firing pin dropping and that sets off a tremendous kaboom here's a bit of a close-up on the optics mount it's a pretty complicated affair here but basically what you have are two different dovetail mounts so you'd have your direct fire sight slide in here your indirect fire sight slide in there and that allows you to use this both in an anti-tank role and in an anti-personnel or embarkment sort of long-range role gross adjustment of your elevation it's done with the the pintle mount on the tripod here so this allows you to pivot it up and down as well as of course changing the angle of the legs and then fine adjustment to the elevation is done with this control wheel here which just threads this up and down yeah I don't quite have that pin all the way through but that's how it all works these were pretty hot stuff in World War two in the Korean War they weren't that great that useful for armor but they were still quite effective on pillboxes fortifications light vehicles and that sort of thing by the Vietnam War these were really on their way out they were being replaced by more effective more modern weapon systems however these do actually still have a role and they are still in use to this very day every winter these are the guns that are used in a lot of places for avalanche control deliberately setting off controlled avalanches before they can accumulate enough snowpack to get really big and destructive so the National I believe it's the National Park Service actually maintains a number of these and that is what they use to set off controlled avalanches so pretty cool on going use a pretty cool use for something that is an obsolete military weapon can use it for basically public safety use today so if you're interested in owning this one whether you need to prevent avalanches at your house or you just want to have a really cool and actually suitable vintage destructive device this is an NFA registered destructive device so as long as you're willing to go through the NFA procedure to own it you can certainly do so take a look at the description text below for a link to James Julia's catalog page on this piece that has their pictures description has a couple other accessories that come with it in addition to the gun itself and value and everything else that you would need to know to place a bid on it either through their website or live here at the auction thanks for watching

Channel: Forgotten Weapons

Views: 861,932

Rating: 4.9584589 out of 5

Keywords: m20, m20 75mm recoilless rifle, heat warhead, recoilless, recoiless, rifle, 75mm, world war, antitank role, Forgotten Weapons, optical sights, wire guided missiles, avalanche control, WP, M18, 57mm, Vietnam War, bazooka, rocket, heat, he, phosphorus, destructive device, nfa, 105mm, m27, vented case, t34, antitank, korean war, ww2, mccollum, kasarda, inrange, inrangetv, super bazooka, jeep, weasel, at

Id: QWR3SwSEdTg

Length: 10min 59sec (659 seconds)

Published: Thu Mar 08 2018

Reddit Comments

[u/The_Real_Mr_Deth]

A snappy salute to Ian of u/ForgottenWeapons from r/warthunder... yet another community who loves your stuff!

[u/Genchri]

All hail Gun Jesus, provider of knowledge and patron saint of gun affectionados... also he loves Swiss stuff.

[u/zayo]

How neat it would be if Gaijin made the shots from those recoilless rifles look like the real thing, with the gas venting back so much? I'd love to see that on the battlefield.

[u/Artyom36]

I've spent hours viewing videos from gun jesus, the knowledge this dude has, it blows my mind.

[u/Marcusporus]

Nothing like my daily dose of Gun-Jesus to brighten my day!

[u/iguanicus-rex]

Forgottenweapons posts are best posts. God bless Gun Jesus....Or Gun jesus bless God...Or Gun Jesus bless himse--you know what, never mind

[u/KriegerKojote]

They also did a video awhile back about a Swedish 20mm recoilless rifle. Pretty awesome alternative to an anti-tank rifle during the Second World War.

Gustav M/42; grants infantry the ability to penetrate 40mm of armor at 100 meters, yet only weighs ~20lbs.

[u/[deleted]]

Sometimes I use Ian’s videos to fall asleep too. Combining guns and history is just the best.