Hi guys, thanks for tuning in to another video on ForgottenWeapons.com.
I'm Ian McCollum, I am here today at Morphy's,
and we have something I'm sure you've already recognised.
This is an HK MP5SD.
This is the integrally suppressed version of,
I'll go ahead and say it,
the best submachine gun ever made.
This was ... originally introduced in 1968
as a follow-on version to the regular MP5,
because there were some special operations sorts of guys in the German military
who wanted a suppressed version.
And so HK went to work figuring out what they could do to make this a reality.
And it's a little more complicated than just tossing a suppressor on the end of the gun,
because ... there are a couple of things that they had to account for.
And one of them is the fact that standard, military-use, 9mm ammunition is supersonic.
And if you want a properly effective suppressed weapon you ... have to have a subsonic projectile.
Otherwise no matter what you do with the muzzle blast
and the pressurized gas coming out of the barrel
you can't avoid the fact that you'll get a sonic crack from the bullet if it's breaking the sound barrier.
And that's louder than you may recognise,
that's a significant element of the noise of a firearm.
So if you want a properly suppressed weapon, it has to be subsonic.
But what if you don't want to have to have two types of ammunition?
You want to be able to use standard 9mm, but make it subsonic.
Well, HK's solution for doing that was to use a special barrel design
where they have actually drilled a bunch of holes right in front of the chamber.
So as soon as the bullet starts accelerating down the barrel,
instead of all the gas pressure pushing the bullet,
a bunch of it is immediately vented out into the rear chamber of the suppressor.
That drops the pressure in the chamber behind the bullet,
and that reduces the maximum velocity that the bullet will attain.
In theory reducing it below the speed of sound.
We'll try that out tomorrow, more on that in a moment.
Now, the original suppressor design that HK came up with used a wire mesh pack basically,
and this was a suppressor design that had been used in World War Two.
The US M3 Grease Gun uses it, if you're curious about that
I have a video on the suppressed Grease Gun that you can check out.
The problem for HK was they found that that wire mesh
got like thoroughly fouled to the point that it was no longer fully effective
in something like 70 rounds, and then it had to be taken apart and cleaned.
And that wasn't acceptable, so they needed a new version of the suppressor.
So, let's take a closer look at the gun itself.
I want to show you a couple of the features up here where it's different from a standard MP5.
And I have a picture of a sectioned suppressor from this
so I can explain to you exactly how they made the final production version.
Just for comparison's sake to start here, this is a standard MP5.
This is actually a semi-auto short-barrelled rifle, but
all the dimensions and layout of a standard MP5, and here is the MP5SD.
So the receiver is the same, the sight radius is the same,
the sights themselves are the same.
However, the handguard has been replaced with this cylindrical model,
and the suppressor sticks out quite a ways.
Now the barrel on the SD is only 5.7 inches long, so it comes to about here.
Really everything from here back on the gun is the same.
So it uses all the same standard magazines, typically 30 round, 9x19 Parabellum of course.
Now it's when we get out here that things get a little bit different.
So, we have this rather grippy handguard,
that's an insulator that's applied to the outside of the actual handguard.
If this looks familiar to you from other places,
it is because ... like the one existing Pancor Jackhammer shotgun
was retrofitted to have one of these grips on the front of it
to give it a little more texture.
So you may recognise this from the Pancor Jackhammer and that's why,
they used an MP5SD part there.
Now the suppressor. That's the real part here, the important part.
You'll notice the very end of this is actually textured, and that's to give you grip
so that you can (there we go) unscrew it.
Because this comes right off.
And if we take a look down there you can see that the barrel is rather shorter than the handguard itself.
Now at the base of the barrel are a number of vent holes
which you just can't see here.
And there's no easy way to take the handguard assembly off.
So instead we will take a look at a cutaway suppressor.
This version of the suppressor was developed between 1970 and 1972
in response to the longevity issues that the original wire mesh type had.
So what we have here is a two-part suppressor.
There's a first chamber back here, that's just an open first chamber.
And that's what takes the gas initially vented when the bullet fires
and just allows pressure to drop to slow the bullet down.
Out here is where the real meat of the suppressor is.
And this is actually sort of a coaxial design where there is an outer aluminium tube,
(the whole thing is aluminium by the way),
and then there is an inner section that is made of actually aluminium square tubing
that is cut and bent into a series of V-shaped asymmetrical baffles.
And so this actually makes it, especially at the time, a very easily manufacturable assembly.
There isn't a lot of stamping out individual baffles and then having to weld them in place.
The whole baffle stack was made as one continuous part
out of plain drawn aluminium square ... tubing.
Now you can see those V-shaped baffles in there from the side.
Those are asymmetrical, you'll notice the top and bottom are of different lengths,
that helps to add turbulence to the gas.
Basically, anything that is going to keep the gas inside the suppressor moving around
before it finds its way to the exit at the front,
is going to reduce the eventual pressure when the gas does come out
and is going to make the gun quieter.
So ... HK is maybe a little touchy about the interior design here.
This picture, by the way, ... was taken at the Mauser museum in Oberndorf by me.
And so HK didn't give me a picture of this, but I found one anyway.
And I think it's a really interesting internal design to the suppressor. ...
I am not a suppressor expert, yet, but it's rather different than a lot of the other designs on the market.
... And dates all the way back to the early 1970s, which is really pretty cool.
And frankly I think it helps explain how the SD achieved its position of dominance in the market.
It really just was an excellent suppressor for when it was manufactured.
So we can go ahead and put this thing back together pretty easily. Just drop that on,
thread it down, and there we go. We're ready to go.
... I'm pretty sure the MP5SD has been featured in every video game ever made,
and I think it's been in most of the action movies ever made.
It is an extremely recognisable suppressed submachine gun
that basically anyone you show this to who knows what it is, they will agree that,
"Yeah, that's pretty much best of breed for a suppressed submachine gun."
There really ... aren't a whole lot of competitors nipping at the heels of the MP5SD.
So it was very cool to get a chance to take a look at this one.
Very happy to find a proper original HK one that I can show to you guys.
And I'm really kind of curious about how effective that barrel is in actually reducing bullet velocity.
So we're going to go ahead and take this guy out to the range
and try it out tomorrow, so stick around for that.
Thanks for watching.