The new Savage A17 uses a delayed blowback action. A small bar in the top of the bolt slides up to fit into a slot in the receiver when the bolt is closed, locking the action. The bar cams back down upon firing to release the bolt and allow the action to cycle, but it delays the action from opening until pressure has dropped to a manageable level.
.17 HMR has never been a caliber that's taken well to semi-automatic rifles—until now.
.17 HMR has never been a caliber that's taken well to semi-automatic rifles, but Savage Arms might have rolled out a new answer at SHOT Show 2015's Media Day at the Range.