Just bought a barely used 2014 date code 9SD.   I'm wanting to suppress it and will need a piston for this gun.   This is my first HK and I'm not sure which LH thread pitch this firearm uses.     I've checked the manual and the box.   No mention anywhere.

I plan on using my CGS Group Mod9 FS.    CGS offers both 13.5x1 LH and 16x1 LH.

Which one should I order?    Also, does the 9SD use an o-ring on the barrel or is that limited to the Mk23 model?

13.5x1 LH, no o-ring on the sd barrel

Thank gents.   Off to buy the piston.    Also need to convert it to a Variant 2 (lefty shooter).    This one came pre modded with the Jet Funnel mag well and the USP Match trigger.

enjoy! a suppressed usp is great fun to shoot