I'm wondering if anyone knows how M855 will work on coyotes from say 25 to 200 yards? I have a bunch of it and would like to use it. BTW, pelts are not a consideration.

Saw a post where it took a couple mags to down a cougar with M855.  It might work on a coyote but it ranks up there with about the worst ammunition made for terminal ballsitics and accuracy, especcialy once you get past the fragmenting range.  Save it for plinking and short range use IMO.  55 and 60 grain ballistic tips are about perfect for an animal that size.

Gonna zip right thru and not expand. May be alright for coyotes though I have seen some run a pretty good piece after being hit with a 55 gr FMJ.
Give it a try on some yotes and see how it works.
TS

I used an AR18 in the early 70's on deer in Central Texas and I personally would not recomend it.  I have not tried any of the newer 75 Grain bullets with a .223.  There are better bullets (i.e. larger calibers).  There is a lot of press about various .224 dia. HP's being used with some success on large varmits.

In Vietnam, at night my old 1st Sgt and some of the troopers would hunt and shoot wild dogs on our firebase (large base).  The .223 was a very poor choice.  They switched to riot guns which were very effective.  The .223 issue 55 grain would wound the dogs and cause a slow death.  The issue 00 Buck was one shot one kill.

CPTKILLER

   .223 is a legal deer caliber in some states.  I have my doubts that FMJ is legal hunting ammunition anywhere though.  

   Find a good whitetail round for this job.  I use Black Hills (blue box) 55gr soft point in my carbine.  Your mileage of course, may vary.  

   If I get more into it I may look for a heavier round or possibly roll some of my own.

You don;t need a heavier round.  Penetraition isn't really an issue with coyotes.  You need to get a bullet that rapidly fragments/expands like the ballistic tip in like a 50 or 55 gr.  These will expand right away before the bullet leaves the coyote, causing enough damage to put the yote down.

Please don;t use that 62 gr for anything living, including self defense.