I've never seen a H&K OEM one. You might check out Bar-Sto, Nowlin & other aftermarket bbl makers. I would think they could whip one on you, IMO.
Sorry I wasn't more help.
Originally Posted By dunndw:
The EFK barrel I have needed a little fine tuning to get it running well with the suppressor on it. Nothing a small hand file couldn't fix, that and range time.
Good deal on one in the EE