watch that again, pay special attention to the second shot. mind you that those old cameras were less than 30 frames per second. so it couldnt be slowed very much. lets say 30 feet in over half a second. thats about 60fps or 20mps. my guess is that those bullets didnt have much more than a primer in them.
in a nut shell, if the glass had failed, the bullet would hardly break her skin.
You're probably right. The impact from a rifle bullet on that close distance would have shot the glass out of her hands, no matter if the glass itself was bulletproof.
yeah also notice that she flinches before the bullet hits glass in all of the shots. real bullets travel faster than sound, even old bullets. thats what makes the bang(sonic boom)
quote form wiki -muzzle velocity
"Muzzle velocities range from subsonic (below 330 m/s / ~1080 ft/s) for some pistols to more than 1,800 m/s (~5910 ft/s)"
at 30 frames per second and with a 300 mps bullet, the bullet would travel 10 meters per frame. would be invisible. in that second shot its clearly visible and moving.
Most handgun rounds today are supersonic, but the .357 magnum was just being introduced in the mid 1930's. It's supersonic velocity was what made it so groundbreaking. Prior to 1930 most of the popular rounds such as the .45ACP, .45LC (long colt, cowboy bullet), .32ACP, .32S&W, and .38 special were all subsonic and typically still are.
The .357 magnum is based on the .38special and they use the same bullet. In fact the .38 can be loaded to the low end of .357 velocities but the resulting high pressures could damage an older gun that wasn't designed to be as strong.
All that said, you don't get a real good look, but the gun looks like a shotgun firing some sort of very light slug load. Probably just a primer like someone said. Even .45ACP, which is nearly 1/2" in diameter and is considered very slow is difficult to capture in flight on film.
Just looked it up and even the good ol' Daisy Red Ryder BB gun is 350fps.