GEMTECH Thread Protectors will... protect your threads.
M13.5x1mm Left Hand: For Sig P226, HK USP9SD, and Smith & Wesson M&P9 SpecOp.
These protectors will tighten down easily onto most any appropriately-threaded pistol or rifle barrel, keeping fine threads from being damaged from bumping around gun cases, or when you're not using your suppressor.
