Controversy always follows the mention of the .17 HMR and Coyotes. Yes, I agree it's light for coyotes. Yes hitting them with something more powerful would be more certain of dropping them where they stand. However, there have been many posts by people that have killed coyotes with them, alot of them in dropping in their tracks. There have been others who have had results similar to yours.
Now, I'm not saying you California boys aren't good shots, but I am saying other people have not had the problems you have. This topic is surely to be a source of controversy every time it comes up. I do admit I have limited experience on game with the .17HMR, but have used the 20 grain on crows and have seen it penetrate through a 5/8 inch pine fence after leaving the crow, the distance being over 100 yards.
If the Coyotes are causing a problem, given the choice of not being able to hunt them because of noise and safety concerns, or using the .17 HMR, I'd use the .17 HMR, and my choice would be the very explosive V-max, because in this case, the bullet doesn't need the risk of a ricochet. Yes, I might wound one, but how many deer are wounded by bow hunters every season? I don't hear the out cry about that.......and around here at least, deer are held in much higher regard than the coyote. I'm sure no one wants to wound game, but it happens, right or wrong.........and with cartridges much larger and more powerful than the .17 HMR
Oh heck, now that I think about it, why don't you bow hunt for those particular coyotes?