The Correct Delta Adapter for a 1/2x28 Rimfire Host
The SilencerCo Delta Adapter AC3 is a 1/2x28-to-1/2x28 O-ring engagement adapter for compatible SilencerCo rimfire suppressors using the Delta accessory interface. Its purpose is not to convert one thread pitch to another. Instead, it changes the effective engagement length of a .6-inch 1/2x28 muzzle thread to .4 inch while adding SilencerCo's O-ring engagement arrangement.
That matters because proper suppressor seating depends on more than thread pitch. Thread length, shoulder geometry, bore clearance, and the suppressor's intended mounting interface all have to work together. AC3 is the correct option when the host barrel is 1/2x28 and the compatible Delta suppressor setup calls for the 1/2x28 O-ring engagement adapter.
What the Delta Adapter Actually Does
The name can be misleading because both sides use 1/2x28 threads. AC3 does not change a 1/2x28 barrel into a different thread pitch. It shortens the usable .6-inch exposed thread length to .4 inch and provides the O-ring engagement used by the Delta mounting system.
The O-ring arrangement is intended to help keep muzzle threads cleaner and help prevent the suppressor from loosening during firing. It is still essential to confirm that the suppressor seats properly, the host barrel has appropriate support behind the threads, and the complete system is correctly aligned before firing.
Compatible SilencerCo Delta Suppressors
AC3 is part of SilencerCo's Delta accessory family for compatible rimfire suppressors. It is intended for use with the SilencerCo Switchback 22, Sparrow 22, Spectre 22, Warlock 22, and Osprey Micro 22 when the firearm host and selected suppressor configuration call for this 1/2x28 Delta adapter.
It is not a HUB / Bravo, Charlie, ASR, Alpha, or direct-thread mount for centerfire suppressors. It should also not be used as a generic solution for every firearm with 1/2x28 threads. Select the adapter around the actual suppressor interface, host-thread length, and firearm configuration.
Confirm Your Host Before Ordering
Verify that the barrel is truly threaded 1/2x28, not 1/2x20 or a proprietary metric thread. SilencerCo offers other Delta adapters for hosts such as the Walther P22, SIG Mosquito, FN Five-seveN, GSG 1911-22LR, and S&W M&P 22 Compact. Those are not interchangeable with AC3.
Before firing, confirm correct suppressor fitment, unobstructed bore clearance, muzzle-thread condition, and manufacturer guidance for the firearm and suppressor being used. The adapter does not replace proper installation, alignment verification, or safe suppressor-use procedures.
Who Should Choose AC3?
AC3 is the right choice for an owner of a 1/2x28-threaded rimfire host who is using a compatible SilencerCo Delta-interface suppressor and needs the .6-inch-to-.4-inch O-ring engagement arrangement. It is especially useful for keeping a dedicated rimfire host configured correctly instead of relying on improvised spacers or an adapter intended for another firearm.
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