Hello fellow arfcomers,
So I'm looking to build or purchase my first 9mm MP5 with the intentions of converting it into an SBR. I've been doing my best over the last few days to research the variations of this iconic weapon and I am beginning to feel a little in over my head. I have no hands-on experience with the MP5 except for a machine gun shoot I went to a couple of years ago and lets face it, the fun switch is worse for focus than alcohol so I didn't pay too much attention to the specs of the gun I had in my hands. I've worked in a machine shop for two years before I decided to become a Paramedic for which I am currently attending school and I am good with my hands, so building an MP5 if it is practical doesn't scare me away.
Firstly, I want to continue my research on the variations of the MP5, for example I am familiar with the concept of the K variation having a shorter barrel and hand guard, but I haven't found if that is the only difference from a "regular" MP5 which I don't know exactly how to define. Also I've seen the term "Reverse Stretch" thrown around but I currently don't know exactly what that means in relation to MP5s. So information on the weapon system itself is where I want to start and if anyone knows some good sources of that information I would be very grateful, and if you just want to share what you know here that is great too!
Secondly, once I know more about the kind of MP5 I want to own, I would like to get some information on the pros and cons of building versus buying and which manufacturers and dealers to look at. The AR 15 has been my weapon system of choice and I have spent years learning about it, but when it comes to HKs and MP5s I'm still lost so any insight from guys in the know would be helpful here. I know it's tempting for the internet fanboys to chime in to tell me that according to Mr. iCanMakeAVideo, such and such is the coolest thing since sliced bread, but I'm really hoping to get some feedback from guys with hands on experience, Thanks.

Thanks guys, I'm looking forward to your respnses

Reverse stretch is standard MP5 rear with 1 rear push pin (vs 2 for K model), MP5 recoil spring and butt stock options, but K length barrel, cocking tube, K carrier. It's a mix and match, but many love these.

Options are:
German K94 or SP89 (most costly). $4k to $5k.

Good contract pistol and carbine models by POF and MKE (may have variations of internals which you may not care about). About $1500.

Atlantic Firearms and DJF make clones, about the same cost as the contract makers.

Gunsmiths assemble them from various parts kits, German or German/US parts or all US parts, by rolling a flat, welding it up with the parts into a clone. You need good TIG welding skills, and some machine shop access to build an HK well. It has been done by amateurs but usually at a group build.  I have had an HK94, SBR'd it, sold it. I have a clone MP5 pistol (all German parts) built by Dakota Tactical using a US flat, extremely well done. There are several clone builders, the cost of a smith built gun is usually higher. $2500 to $3k depending on the model, how many US parts.
My D54P clone pistol:

My SP89/MP5K-N conversion by Murray Urbach with registered sear:


HKPRO has a clone section, as well as posts here for more info.

Top to bottom:
Mp5
Reverse stretch
Mp5k
Mp5k with shroud

Love my recently purchased MP5 and I guess to answer the question of to build or buy I would direct you over to HKPRO.com.

There a several vendors there to compare and I think there are a couple active threads where this question is being discussed. What I took away from those threads was if you want to spend the time, are good at welding and can get information on the various jigs that are 'needed'  than have fun with It but it will be a large investment in time and money.

I believe there are builders that will take your parts and build it for you. This would save you the learning curve of building your own and allow you to have your selected parts, not sure on costs.

I purchased my MP5 from DJ Getz and am very happy with it. I don't have a problem building my own AR but when it comes to the MP5, they aren't as modular as the AR platform. (no welding, jigs, etc )

That k isn't yours as the one pictured is a sw5 that had a cast receiver and was built like a tank..   But yours looks just like it...  :)

FYI both guns are on schedule for Friday delivery! Whoot whooooot!

Thank you all for your responses, I've learned a lot. Feel free to share any more information or pics as I haven't finalized my decision yet.

ETA: For me and I think for most, the MP5 is so desirable for its small size, sexy looks (if we're being honest here), and light weight. These things considered, what would lead someone to get a full size MP5 versus an K or reverse stretch? is there a significant difference in velocity, performance, or accuracyof a 9mm from the two barrel lengths?
Thanks again.

I have a 94FS (MP5 clone) from DJ Getz

I would pick up a pre built K or reverse stretch from DJ Getz, and get it on a Form 1 ASAP. E-files are coming back in under 4 weeks right now, which may be the quickest we will ever see. My reverse stretch should be approved in the next 7 days!!!

I like what I've seen of DJ Getz Firearms' work and he seems to have a good reputation which is definitely worth a lot. Why does he sell his firearms without firing pins?

It's not a complete gun, therefore, not subject to a gun tax of some sort, imposed on the sale of complete guns.  Smart business.

Ah, thanks for that bit of information. Love the business tactic.

So unless someone can give me a good reason to go with a full-size, I think when I have my pennies stacked together I would like to get DJ's 89K reverse stretch pistol followed by a form 1 sbr tax stamp and lots of fun. Am I on the right track?

Very good track.


Just remember, these suckers tend to multiply.

DJF has a sale going on for SW/Coharie guns on hkpro. Under 1100.00 for everyone but the trigger group.

Holy smokes, that's hard to pass up! How does quality of SW/Coharie compare to DJF's work?



Haha, then I'm in trouble 'cause we are already pushing four 24-gun safes...