https://greyhive.com/videos/watch/e057ed16-3f39-41e0-a37f-4a53b7b5da2c Function test on 55gr subs w the Mk57 upper. Ran flawlessly minus the bolt not locking back after the last round. Personally I believe once I have a trigger in my Mk57 lower the bolt will lock back every time regardless of ammunition grain weight. Like, comment, subscribe, and let me know what you think. Thank you for the continued support! Stay tuned!! Tue, 03 Nov 2026 15:14:58 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://greyhive.com https://greyhive.com/lazy-static/avatars/5746210d-885d-44b2-9be0-92bf1e4d34df.webp https://greyhive.com/videos/watch/e057ed16-3f39-41e0-a37f-4a53b7b5da2c All rights reserved, unless otherwise specified in the terms specified at https://greyhive.com/about and potential licenses granted by each content's rightholder.