Review: H&K MP5K Briefcase And My Modifications

    Last year Altra Firearms came across a collection of H&K MP5 parts. One of which was a genuine H&K MP5K briefcase. Now Rusty S. posted up a lightning review of his MP5K briefcase about two years ago. I had always wanted an MP5K Briefcase and there was one for sale very close to me. My friend Scott had posted it up on various groups so I contacted him and I bought it from Altra. The briefcase cost me $2,000. I have heard people say they are $1500 but I have not see them go for that cheap. I knew of one other person near me who had one and he spent $4,000 for his briefcase. Sadly he sold it before I acquired mine.

    The H&K Briefcase is actually specially made by Hofbauer in Germany. Here is a link to their UK website. They still make this case under their Citybag line of cases. Now I am not sure what Hofbauer made for H&K and what H&K made themselves. Obviously It would be easy to order a custom molded case that suited their needs. When you remove the handle there are four indentations where the case is molded for the handle and there is a slot for the trigger linkage.

    Obviously there is a hole in the side of the case for the bullets to fly out of. I think Hofbauer made the case to H&K’s specifications and H&K made the the handle and all the metal internals.


    How Does The Briefcase Work?

    The handle of the briefcase is fixed. This is due to the linkage and trigger mechanism hidden inside the handle. The left side of the handle can be removed after you remove the safety.

    Briefcase Variants

    My briefcase is a little different from Rusty’s. The arm that pulls the trigger is straight whereas Rusty’s has a crooked style trigger arm.

    Here is a crooked style arm.

    The reason for this variation is due to the difference in MP5K lower receivers. The older SEF style lowers only have a selector switch on the left side of the gun. Navy style lowers have ambidextrous selector switches and would interfere with the trigger arm.



    If you look at Rusty’s briefcase he is using an MP5K. One issue I had with this is that I wanted to use an MP5K-PDW. The metal shroud that protrudes from the side the briefcase does not allow PDW style barrels to be used.


    Rusty’s briefcase handle is also different from mine. It looks like it is machined and uses phillips screws rather than the slotted screws that mine has. According to Scott, these are not H&K briefcases but replicas by Tom Bailey back when he ran Special Weapons.


    Problems With The Briefcase

    For those with a Briefcase you will know the pain that comes with installing your MP5K into the claw mount. Even without the factory cleaning kit (the green box bellow the gun) installed in its holder, it is impossible to get the MP5K into the claw mount. I would have to unbolt the claw mount from the case, install the claw mount onto the MP5K and reinstall the entire gun and mount into the case.

    Another issue, which I mentioned earlier, is the fact that you cannot use an MP5K-PDW. The first problem is the barrel. The MP5K has a flush barrel with the front sight. A PDW barrel sticks out. The metal shroud was designed for MP5Ks and not PDWs. The second problem with using a PDW is the stock. MP5K folding stocks all fold to the right. Since the briefcase trigger arm sits on the right hand side of the MP5K, you cannot have a folding stock mounted on an MP5K-PDW and use it inside the briefcase. You end up having to remove the stock and use a sling end plate.

    Other issues are clearing malfunctions. This is problematic since the ejection port is on the right. H&K should have flipped the MP5K around and face the opposite direction. Then you could have a folding stock and clear malfunctions much easier.

    Modifying The Briefcase

    Once I saw how the briefcase works I immediately had some ideas of how to solve some of the problems. The long metal shroud is an easy fix and other briefcase owners have done the same thing. They chop the shroud down a bit to allow the PDW barrel to fit. You just have to chop about an inch off the shroud to allow space for the tri lugs.

    The other modifications required the help of my machinist friend Keith. I wanted to replace the claw mount for an easier QD mount. I got the MFI Ultra Low Profile rail, made exclusive for

    Then I used a Midwest Industries Aimpoint T1 mount that I had lying around. Since the MFI rail is rather short, we had to machine the corners and the latch to clear the rail.

    You can see the latch just clears that part of the rail. If we didn’t shorten it, the latch would not close all the way.


    Next we milled the top of the mount and cut an aluminum bar that will bolt to the case and the mount.

    It was Keith’s idea to counter sink the mount into the aluminum plate that way there would be less stress on the bolts of the mount when the MP5K is fired.

    Next up was to install a brass deflector. HK has a curved brass deflector that is bolted to the side of the claw mount. I was unable to reuse this because of where it attaches to the claw mount. It would have to be attached to the low profile rail on the MP5K and that defeats the purpose entirely.

    We ended up making a deflector out of a sheet of brass. So it is literally a brass deflector.

    I had Keith make a threaded steel barrel extension so that I could attach a suppressor to the PDW barrel through the opening in the side of the briefcase.

    Yes having a suppressor sticking out of the side of the briefcase diminishes the discreteness of the briefcase but I wanted to do it because I can. Also with the briefcase closed and the suppressor attached it should be very quiet when shooting subsonic rounds. The suppressor would help with the report of the gun shot and the briefcase would muffle the sound of the action.

    The last key to this briefcase puzzle is from Sig Sauer. Their MPX/MCX folding stocks fold to the left of the gun. Not only do they fold to the left, but they are rather narrow. There is enough room in between the case lid and the MP5K to accommodate the folding stock. All I had to do was get a picatinny rail onto the back of the MP5K. I ordered a steel endplate from HKParts and had Keith mill off the sling loop protrusion then drill and tap the plate for a modified Magpul MLOK rail.

    The last upgrade I will do will be to attach a small rail in the front of the handle so I can mount a small compact laser. Aiming the briefcase is a bit challenging. There is not much to go by other than walking your rounds onto the target. Spray and pray is not a technique I like and a small laser would help a lot.

    Now to Test Fire The Modified Briefcase

    I met up with Scott to use his modified Zenith Z5P which he made full auto with a registered sear pack. The brass deflector was giving us a couple of malfunctions and once I removed it, the setup became reliable.


    As expected, the suppressing the briefcase worked better than I had hoped. The camera audio does not do it justice. Hitting the steel targets was louder than the gun. I shot the briefcase horizontally as that is how I see most people shoot the briefcase in videos. However Scott believes this is not how H&K would have instructed it to be used. It would have been be carried vertical, brought up and supported at the bottom with the support hand while fired. I will tweak the brass deflector in hopes that it will not cause the brass to bounce back into the action. So far all the modifications I have done, except for shortening the shroud, are not permanent. I can remove them and revert the case to its original configuration.

    Nicholas C

    Steadicam Gun Operator
    Night Vision & Thermal Aficionado
    Flashlight/Laser Enthusiast
    USPSA competitor

    Any questions please email him at [email protected]