I’m a fan of the Roller Delayed Blow Back firearms for a while and have had opportunities to own and shoot ones from HK, POF, and PTR. I knew the rollers were locking the bolt head in place but never really understood the details of the action. I’ve tracked down two great videos to help show you what is going on.

Forgotten Weapons
In this short video, Ian @ Forgotten Weapons does a great job explaining just how this system works.
MouseGunner
This is one of MouseGunner’s cool x-ray renderings where he shows the MP5’s action at work. He’s done this for other weapons as well and watching the weapon operate really helps.
I hope this helps you out. Be sure to subscribe to both guys’ channels – Forgotten Weapons and MouseGunner.
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