Works perfectly in my ar10 and sr25 - Armaspec AR10 Gen4 Stealth Recoil Spring

A note for some of you with cycling issues, this works entirely different than a buffer/spring. This has a stem that travels up through the BCG as part of it's cycling process. If you have a non-standard bolt, it could be possible that the stem from the Recoil Spring won't go through the hole in the BCG. Test the bolt and Recoil Spring before assembly or firing. I've found at least two bcgs, including one from PWS that are not compatible to the way this device functions. I hope this helps.