The 17Mach-IV, soon to be mass produced Remington 17 Fireball, is a super night time, under 150 yd, Predator rifle cartridge. Mine with a 2?" barrel is quiet enough to shoot without ear protection, although I don't advocate doing so. Consider its 17 to 19 gr of powder pushing a 25 gr projectile around 3800 fps, against a 50 gr projectile needing 26 + - gr powder to get it to 3500ish fps if that. The noise factor of the 221 based cartridges are second only to smaller, less powder using Hornet style cases, therefore less spead(in most cases) and or Rimfires, therefore less noise. Don't like rimefires for coyote sized animals, althought they may do the job, my opinion is of the negative!!
The 204 when pushed to 3900 fps is as loud if not louder than some 223 loads. Still nothing like a 22-250.
Sad part with a 17 Fireball, if you don't reload, the only bullet choice i've heard of is a 20 gr vmax, and that won't cut it for humane kills on coyotes /ubbthreads/images/graemlins/grinning-smiley-003.gif
Later
DF2