In this video, it is fairly easy to see that both the Sig M400 and Sig 516 are cycling at approximately 830rpm and display a small amount of bolt bounce in stock configuration:
Please see my previous SHOT high speed video post for more information. Unlike the video in that link, the rifles in today’s post are being shot by the same person. Here’s some of what I had to say in that previous article:
The rate at which the bolt carrier assembly recoils rearward can have an effect on reliable extraction and ejection, even if extractor and ejector dimensions and springs are absolutely correct. The period of time during which the bolt is behind the stack of rounds in the magazine, neither traveling rearward or forward, has an effect on reliability in that the magazine may not have enough time to push the next round into place before the bolt comes forward again, resulting in a “bolt over base” malfunction that is most commonly seen on suppressed rifles, as they have much greater rates of fire. Also, high forward bolt carrier velocity can result in extreme bolt bounce, as noted previously, while low forward bolt carrier velocity could mean that there isn’t enough force to overcome strong magazine springs, dirt or debris in the action, etc.