It is not the caliber; it is the relative cartridge size that put them in the same class "COMPARED" to your suggestion of 25-06. Which is twice as huge.Kind of a weird grouping in my mind. Why a 256W when the others are 22cal? 25-06 may be one to look at if you want bigger cal but still extremely accurate and fast…maybe a 220swift…fasted factory cartridge.
I tumble polished a bunch of 5.7 brass and they looked like crap. That's when I realized they had a coating on them. I back burner them since I don't own a 5.7 (yet) and I plan on a soak in some acetone and a re-tumble.The 5.7x28 was plastic coated brass (might still be) for extraction purposes. It wears of patchy after a few reloads - MEK peroxide with finish removing it. Chamber pressure are still high enough at unlocking and moves the shoulder forward, so you will be full length sizing the brass every time in autoloaders. I helped a guy on gunbroker figure out loading for it IIRC he had the FN pistol.
I'd bet money these will fit your magazine.
I'm near 100,000 rounds of 44 Mag shot in the last 30 years. Most all of it was my own cast bullet 245 gr Keith Lyman "# 429421". From a good handgun they will shoot threw an elk, often found under the hide on the off side