I'm the very luck owner of a new HK SP5K pistol and had a great first outing.  As I'm looking at upgrades I was hoping someone could tell me what magazine will fist flush with the pistol grip.

I appreciate the help!

I made the sling myself with 1" and an HK sling.

The 15 round magazine is shorter, the 30 round is longer. I haven't tried any 20 rounders to know how close they are.

As far as upgrades go:

Replace the rear sight with the correct mp5 one if you go to sbr it.

Install the paddle mag release, they have a drop in kit.

Shoot the hell out of it.

As far as other upgrades get a b&t replacement barrel or have someone like TSC Machine cut down a mp5 barrel to mp5k specs and have one of them installed. You can always have it remarked mp5k as well.

The best setup is going to be sbr'd with the front grip like a mp5k should be. Adding a 3 lug and a suppressor helps too.

HK also makes 10 rounders for ban states. You could try one of them as well if the 15 is too long for what you want.

Does the top rail come stock with the HK?   Looks useful.   Thinking about buying one and sbr it.

I picked up a USA made 15 rounder from HKParts, looks pretty close to the right length.