jimmy101 wrote:About the same as the 70,000 in the OP.
I'm very suspect of that number. Watching the video it's hard to tell precisely what it is they're using to measure that speed, but I have a sneaking suspicion that the device is counting dimples as they go by rather than actual rotation. If so....
[pause while Dave finds a golf ball]
...Then the number would actually be on the order of 2,200 rpm. A very reasonable number, IMHO.
To get a bent barrel to impart spin doesn't that require some blowby? A tight fitting ammo wouldn't get much spin from the bent barrel.
True, but the same could be said of ANY system. You simply aren't going to see backspin in a barrel with a tight fitting projectile regardless of how you're getting it to actually spin.