The SilencerCo Piston (brand part no. AC59) is a replacement piston built for the Osprey and Octane suppressor lines, chambered for 9mm and threaded 1/2×28 to connect directly to SilencerCo threaded barrels. SilencerCo machines the piston from 17-4 stainless steel and heat-treats it for maximum durability under repeated cycling. The piston is the working half of the Nielson device, moving to enable semi-automatic cycling and unlock the pistol barrel under recoil when a suppressor is mounted. Shooters running a fixed-barrel host should pair this piston with a Fixed Barrel Spacer rather than use it alone. Among Class 3 parts and accessories, this piston favors Osprey and Octane owners who need a genuine replacement part to keep their host pistol cycling correctly.

Key Specifications

• Built for 9mm hosts.
• Threaded 1/2×28 with female threading that connects to SilencerCo threaded barrels.
• Fits the Osprey and Octane suppressor lines.
• Machined from 17-4 stainless steel.
• Heat-treated for maximum durability.
• Functions as part of the Nielson device, enabling semi-automatic cycling and barrel unlock under recoil.
• Fixed-barrel hosts require a Fixed Barrel Spacer used alongside this piston.

Frequently Asked Questions

Is this piston itself an NFA item? No, it is a replacement part for a suppressor host and carries no separate NFA paperwork of its own.

What suppressors does this piston fit? SilencerCo’s Osprey and Octane lines, threaded 1/2×28 for 9mm hosts.

Buy the SilencerCo Piston

A genuine replacement piston keeps an Osprey or Octane host cycling the way it should. Order it from our Lubbock, Texas gun shop for fast shipping.