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 Company
where they have started doing some kind of bigger guns.
This is a Swedish made Bofors 40mm anti-aircraft gun, and this thing was developed in the 1930s.
And it was adopted by the US Navy in 1938, and by the US Army in 1941,
and by almost everyone else in the world too at some point. This thing saw service in
all fronts and on both sides of World War Two.
This thing is actually a machine gun as well as being a cannon. So it's 40mm,
but to put things in perspective what we're talking about is a roughly...
It's a 4 pound shell, each actual cartridge, and the projectile part is about 2 pounds.
So just under 1 full kilo of projectile being fired between 2,700 and 2,800 feet per second.
So that's the same muzzle velocity as an M1 Garand, a .30-06 rifle,
and you're getting that out of a 2 pound high explosive projectile and you're getting
2 of them every second. This thing fires at 120 rounds per minute, because it is also a machine gun.
So for the US, and really for everyone else who used these things,
this was a piece of intermediate level anti-aircraft artillery.
This filled the gap between a large anti-aircraft gun (something like a 90mm or a 3 inch
anti-aircraft gun, which could fire at, say, bombers at high altitude),
and on the small end something like a .50 calibre machine gun set up for anti-aircraft use.
This fits right in the middle.
(And it's really cool.)
Now when the US adopted this thing it was being manufactured by Bofors in Sweden,
and it wasn't exactly a high-volume sort of production.
In fact I think kind of from the US perspective they looked at this, and they're like Bofors must be this,
like, sod roofed, old-style, you know, ye olde factory with like workers with leather caps,
and little teeny bifocal glasses, and anvils, and hammers, and files and stuff making these guns.
In reality, they were magnificently made guns. They were handcrafted, they were excellent.
And this is in fact an original early Swedish production one.
But the US needed more than Bofors could be producing, especially in time of war.
We didn't want to have to be buying these things from the Swedes at, you know,
expensive manufacturing costs, and then trying to ship them across the Atlantic Ocean,
or even just transporting them from Sweden somehow into Europe, like this is gonna be difficult.
There are submarines and Germans around.
So instead, the US bought ... licensing rights to manufacture these in the United States.
And in fact, the Firestone company, now known for tyres, manufactured the carriages - these wheeled assemblies.
And Chrysler manufactured the guns. During World War Two Chrysler built 60,000 of these things. That's just...
that's a hard number for me to even wrap my head around (and by the way, 120,000
barrels, because every gun they made, they made a spare barrel for it as well).
As I said, these would see service in all theatres, but it was in the Pacific that they were particularly effective
and necessary. By the time these were actually in the field for the US it was basically 1943,
and the height of German airpower had really come and gone. And the US, you know,
this wasn't so critical in Europe, still useful, but it was in the Pacific where it was really essential,
where these were used by US Navy vessels as defence against Japanese air attack.
All right, let's talk about how this thing actually works, because it's not quite what you might expect.
This requires a crew of three men, you'll notice there are two seats.
That's not because you have a redundant operator, you need both of these guys.
So what's going on here is crewman number one
... is sitting over here and he controls the gun's traverse, pivoting it around side to side.
You'll notice he has a spider sight to target whatever aircraft they're trying to shoot at.
Operator number two sits over here and his hand wheels control the gun's elevation.
He also has a sight, he also has a foot trigger and he's the one who fires the gun.
So guy number one over here is constantly just keeping the ... traverse on the airplane, that's his only job.
Guy number two only has to deal with the elevation of the gun and firing it, but firing with your foot.
That's not a particularly complex matter, when the sight's on the target, push the trigger.
Guy number three would be back here and he's responsible for actually loading the gun.
This thing was fed with 4 round stripper clips, and it would actually fire faster than you could load it.
This was the sort of thing where you'd load in four rounds, and then when you had
the gun on target, the ... primary gunner would fire a burst, probably all four rounds,
and then while they're reacquiring the target, the loader shoves another clip of ammunition into it.
This thing has a pretty fast rate of traverse ... on the M2A1 carriage, which is what we have here,
(and this was updated as aircraft got faster and faster), this thing - every full rotation of these handles
gives me 17 and 1/7 degrees of rotation of the whole gun.
The previous ... M2, the basic version of the carriage, it did 6 degrees per revolution.
So they about doubled, almost tripled, the rate of rotation. Now, this thing can do a full 360,
there's nothing to stop it (except the wall behind me), and it can go from
pointing straight up 90 degrees to negative 6 degrees downward angle. You could use this in
a direct fire role, and it was. This carriage, of course, is set up for anti-aircraft use.
But they did make both high-explosive, which was I think the primary ammunition used,
and they did also make an armour-piercing ... projectile for these things. And
you know, a light-skinned vehicle? This could do some serious damage to a light-skinned vehicle.
Alright, so feeding this thing is done up here. This is actually just a cover
over the clip loading machine. This has a mechanical setup here to pull cartridges down off the stripper clip.
You don't exactly just thumb them into this thing. So you put a clip on here in place
and let the gun do the rest.
Now it's kind of hard to see because we've got this ejection chute, stuff on the back of the gun in the way,
but this isn't an anti-aircraft gun, like say a 20mm Oerlikon, which is basically simple blowback.
This is much more like a standard artillery piece set up for rapid fire with a loading operation.
This has a vertically traveling breech block which is right up inside here.
So that breech block is going to slide up and down to lock the cartridge in place, and then it slides open,
kicks out the empty cartridge, which is going to come out through this ejection...
Well, it's going to come straight back here, it's gonna get hit by this chute, and funnelled down to here,
whereupon it skips down into this chute, and goes zwheee
right out the front of the gun under the barrel.
You can see a cooling cut-out here for this big ol' recoil spring. So the whole barrel reciprocates backward
when the gun fires, and that's the energy that is used to ... open the breech block,
feed a cartridge, and then close. This is like a giant semi-auto falling-block gun.
Alright, something else that I want to point out. This gun has a lot of recoil when it fires.
Enough that they put outriggers onto it. There's one over there (stop that),
there's one over here, and then there are outrigger feet on the front and the back of the carriage.
So, in order to safely fire this, you have to set this whole thing up and we didn't quite do it for one good reason.
I'm reading through the manual, and you are explicitly warned not to mess with the suspension setup
unless you have two guys adjusting it and two more dudes holding the thing in place. Well,
I don't have a whole gun crew at my disposal to set this up. So the way this actually works is
these axles actually pivot. The front axle pivots forward and the rear axle pivots backward,
which lowers this whole carriage down towards the ground to lower its centre of gravity.
You can see the outrigger here, that's at its lowest depth of travel and it's almost a foot off the ground.
So, in order for this to actually be set up you have to hold the gun in place,
pivot these wheels up and out of the way, so the guns actually resting on these pads.
Now the reason that they did that is because the point of the pads is stability.
And the best way to get stability is to lower this whole thing down towards the ground.
Not to put it on nice tall feet, that's going to make it just wobble around a lot more.
... You have to make sure it doesn't tip over, yes, but you also want to make
sure that it doesn't rock when it's firing, because it's a machine gun.
You want it to be stable and put the shots exactly on the same place every time
so you can try to actually hit a fast-moving aerial target.
(This thing's just really cool.)
So a few other bits of history to touch on. First off,
like I said, this was used by more than just the United States, the British actually also used these.
And in fact these Bofors guns are credited with a couple of V1 rocket bomb shoot downs, or kills,
potentially making them one of the very first anti-missile weapon systems, which is kind of cool.
In addition, let's see, the the Bofors system would be enormously successful worldwide, of course,
and would go on to be successful after the war. So in 1947 they actually made a serious update to this whole contraption.
They realised jet powered aircraft were starting to make this sort of gun a bit obsolete, and in an effort to to kind of
delay that obsolescence the new version had a longer barrel, it used a more powerful cartridge,
they upped the rate of fire from 120 rounds a minute to 240 rounds a minute, so doubled it.
And perhaps most significantly they added ... a gas engine and electric motors to this
so that you could have one gunner with a couple of control wheels doing everything,
instead of trying to coordinate two separate guys to do the aiming, so.
That gun, I mean, I think those guns are still in service today in various militaries.
These are actually still in service even with the US, in the AC-130 gunships.
We have Bofors 40mm guns up in those guys, and people, they're still very effective.
There's nothing wrong with these things to this day.
I also want to touch on the aiming.
... You can see the two spider sights set up here, and in World War Two that's what you had.
However, even in World War Two they had a very early system of networked, and computerised,
and motorised systems for these guns that you could actually get one
computerised, what they called a director, a fire director, a central aiming device,
then you'd have a guy actually aiming at a target, and you could actually wire it up to four separate Bofors guns
and slave them all to this single director and use them in that way.
And that's just super cool, that that sort of technology was available and actually in use in World War Two.
Well, thanks for watching guys, I hope you enjoyed the video.
You know, a gun and carriage system like this is just so complicated that we could spend hours
talking about every little nuance of the system. Everything from how the outriggers actually fold up
during travel, so that there's no possibility of them coming loose and, you know, causing you to
careen off the side of the road. To how the sights are zeroed, how the feeder works,
everything about this gun is - I mean, there's just so many mechanical systems on it.
But hopefully you enjoyed getting just a brief overview and a little bit of a historical taste for the 40mm Bofors.
This thing is actually for sale at Rock Island. It is a two stamp gun, as such things are called,
because it is both a destructive device and a machine gun. So it is registered per the National Firearms Act.
But anyone who's willing and able to undergo a background check,
if you want this thing in your garage, well, welcome to America.
So you can see more information about it, you can see Rock Island's pictures, their description,
their value estimate, all that sort of stuff through their on-line catalogue. If you take a look at
the description text below you'll find a link that takes you to ForgottenWeapons.com,
and from there you can link over to Rock Island's catalogue page.
Thanks for watching.