Started as a Hog Hunter in .223, shot fine and extracted steel and brass with no problems. Rifle was rebarreled to .300 Blackout with a prefit, headspaced with Forster gauges. The gauges extract just fine, especially after the extractor was replaced with a brand new one and the extractor detent with a .140" ball. With a dummy round (S&B new brass, 147gr pulled bullet) the bolt doesn't extract at all and the dummy has top be tapped out with a wooden dowel. To be specific, almost any pressure at all on the dowel, even just letting the dowel drop an inch pops the dummy loose. Pulled it all back out of the chassis, checked screws and rechecked headspace. Again, the go gauge extracts with no issues, the dummy doesn't. As far as i can tell it seems like maybe the bolt isn't grabbing the case head at all?

What did I screw up?

Disregard, not my screw up. I just mic'd the shoulder on the S&B brass and it's too short. The Savage, not having a controlled feed, it clearly kicking the dummy too deep in the chamber for the bolt to grab it. I tried with a Remington 220gr OTM with a proper shoulder (mic's in spec, visibly the shoulder is higher and sharper) and boom, extracted with no issues.