What upgrades to the sp5k are necessary to clone an mp5k besides sbr'ing?

1. Barrel swap with a tri lug barrel
2. paddle mag release
3. ?
4. ??
5. ???

$ and a competent smith.

Send to TPM Outfitters and be done with it.

It somewhat depends upon what model MP5K you want to mimic.  However, lets assume  you want to go to a MP5K-N based on your 3-Lug barrel comment and using a demil German MP5K-N kit for german donor parts.

1. Press out original barrel from SP5K.
2. Remove MP5K-N barrel from demill German MP5K-N kit.
3. Remove triple frame front sight from MP5K-N barrel.
4. Install and pin MP5K-N barrel into SP5K trunion
5. Reinstall front sight triple frame front sight.  (barrel has to be rotated for reinstall and repin operation so sight frame has to be moved as well)
6. Mill out protrusion/nub in receiver under rear sight base so a full auto carrier will fit.
7. Weld over SP5K markings and reengrave MP5K-N.
8. Install paddle mag release (either spring loaded version or drill and weld version)
9. Refinish receiver.
10. Clip and Pin MP5K grip frame housing from demil kit.
11. Install sear pack and stock.
12. Install appropriate number of 922r parts if going SBR route so as to have no more that "10" evil foreign parts.

Barrel swap if you want a 3lug version. Some can weld a 3 lug to the end of the existing barrel but personally I'd just swap it. B&T barrels seem to be a good middle ground being a licensed partner to hk. A real mp5k 3lug barrel is going to be very expensive. You can also go with an american made barrel which will help with 922r. The last option is to have someone like TSC machine convert a mp5 barrel to mp5k specs. He cuts down a full sized barrel which is a lot cheaper. This way you end up with a german barrel.

Paddle mag release is drop in on the sp5k which is nice. Past that some 922r parts and sbr it. Also from memory the rear sight is wrong for some of the mp5k models but it takes seconds to swap with the right one.

Options would be remarking the gun mp5k(which requires a refinish), modifying the bolt carrier to have the full auto trip or replacing it with one that has it(rcm makes one that clears the block in the receiver, others mill a slot in real hk ones). Mind you this would just be if you want to make it a sear gun.

For doing the work you have a lot of smiths with good reputations. TPM, S&H, TSC Machine, IGF, Tunner(although I don't know if he is accepting work), etc.

Personally I use TSC Machine. Mike and Tammy are good people and will answer questions. He did my sp5k and has a hk94 he converted to a semi auto mp5 of mine waiting on a forum 4. They have also done a few refinish jobs for me over the years.

Thanks for the info guys, I guess its not as many parts as I had anticpated.

I'm gonna start buying the parts and once I have everything, send it to one of the smiths you guys recommended.

Are the original h&k mp5k barrels chromelined or they are all nitrided?

Neither, they're unlined. The finest French steel cold hammer forged in Germany.

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I had the works done to mine.
B&T Barrel
Mag release
Re-stamping
SBR engraving

ETA:  I would avoid IGF right now.  Jayson is having some health issues and is way behind on work.  He did a wonderful job on mine but it took about 5 months.

HK and B&T

Perfect combo

Its worth saying that with a lot of the more well known hk smiths you can expect a few month wait. This is the same with a lot of other gunsmiths as well. When I had practial solutions rebuild a m10 for me a few years ago I think I was quoted 3 to 4 months. You want to see bad look at the guys having mikes machines, tsc, or some of the others build hk21 guns(or hell the price of a barrel for one of them). Those guns can easily take over a year once they have your order/parts.

Sadly my sp5k is still waiting on a form 1 or I'd post a photo. I could show off a hk94 that TSC made into a semi auto mp5n. Actually have another hk94 that should be at his shop over the next few days along with a mp5sd parts kit.

FWIW- I am setting up an SP5k as a sear host. To keep it simple, I am not replacing the barrel. So, I;

Bought a 4pos MP5k trigger housing and had it clipped & pinned by TSC
Bought a SP5k bolt carrier in full auto profile from RCM. (my initial route was to have the original semi-auto carrier welded but that turned into a steaming pile of shit)
Had a paddle mag release installed by TSC
Bought an SB pistol brace.
Keeping my host gun a "handgun" so no 922r, no SBR

$775 (including the fucked-up semi-auto carrier weld job) + $2,100 for the barely used SP5k

I can still buy a folding MP5k buttstock and VFG as long As I make sure to ONLY use them in conjunction with my Registered Sear.

Not a true MP5k because of the muzzle profile and the markings but neither is ANY sear host with a "shelf" really.

If you don't mind sharing... what happened with the carrier weld job?

I have welded up HK rifle carriers in the past without issue but have never welded up a MP5 carrier.  It seems like it should be a pretty straight forward job but what happened on yours?

I plan on doing all the work myself (barrel swap, weld/remark, paddle, etc.) but if there is something out of the norm with the SP5K carrier that makes welding it a challenge I would be interested to know what happened.

I am still on the fence whether I want to weld the carrier to just mill the pin out of the receiver and use a factory german MP5K carrier.

I just had S&H reweld my 93 and ptr pdw carriers, both look great but havent shot them yet. Was $70 each plus $10 shipping, I have two semi hk carriers I might send in as well that I got with two fbi semi parts kits.

Sorry I took so long in responding. I am not sure what exactly happened but the locking piece will not fit into the welded carrier I received back from the shop that did the welding/milling. I tried three different locking pieces and none of them will fit the newly welded carrier. All three are interchangeable in other carriers (one welded, one semi and one full-auto). There is nothing obviously out of spec with the problem carrier. The shop that did the welding has been responsive and I am sending it back to see if they can figure it out.

Just speculating, but one opinion I got was that the heat from welding may have distorted the carrier ever so slightly but just enough to keep the locking piece from fully seating.

I will update this thread once I hear back from the shop that did the work.

UPDATE- The shop exchanged the welded carrier they sent me with another one that fits and functions just fine. They didn't elaborate on what was wrong with the first one but were very responsive and made it right. I am not naming names because I don't want to give anybody cause to be worried about doing business with a stand-up vendor.

Still, my personal, non-professional, opinion is that I just don't like welded carriers. I have two guns that  run them but I really prefer a carrier built with a full-auto profile from the start. Preferably HK factory but as long as it is built right, it doesn't make much difference to me. Again, just my ignorant opinion YMMV.