So, here's a new wrinkle:
Someone on another forum just shared with me a formula for calculating bullet RPM. 12 / twist rate * velocity *60
Based on what little chrono data I've been able to find on 110gr .300blk, it looks like 1950fps muzzle velocity would be very optimistic on a 6.75" bbl, with something in the 1900-1850 range more likely. According to the formula shared with me (12/5*1950*60), that works out to 280,800 RPM, worst case. The Hornady guy was only worried about RPM above 300,000.
Was the Hornady guy calculating based on muzzle velocity for a 16" barrel? It looks like it. I've seen 2300 FPS listed as the MV for 110gr V-max. 12/5x2300x60=331,200 That's almost exactly the figure the guy quoted.
It's looking more and more like the two incidents I've found documented on the internet were caused by first, a specific 125gr all-copper "slotted" HP bullet and second, a frangible bullet (which I've always read should not be used with a suppressor, in any caliber).
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