skin290 is onto something.
when i think "varmint" i think pdogs. in which case i'd go with 20" or 24"... if i had a choice for something i'd use past 400 yards for varminting i'd go with a 26"... i'll take all the velocity i can get. i've shot them out to 700 just last year.
if you're thinking coyotes i'd call them predators also. in which case a 20" for shots out to 400 is a good bet. anything 200 and closer is a 16" for me. the suggestion of a SPR in 18" for use to 400 isn't a bad one.
assuming you aren't shooting at great length, i'd go with a 20" heavy barreled unit. don't let anyone kid you, after you get used to a little more weight, you'll barely notice it. the difference in weight for short barrels when compared to standard barrels is slight.
HTH. just my two cents.
septic tank
FYI - i take 24" units out west for pdogging to shoot of bipods and/or bags. i also take my 16" rig with the EOTech for close work.
fun. fun. fun.