30-06 sounds a little big, but I use a .308.. I hand load some 110 grn varmint heads. (I also use CCI velocitor .22 lr's if I'm shooting under 75 yrds.) Those things do a number on groundhogs. I don't know if a dog whistle will work. I just give them a quick "yo" and they stand up. Sitting and waiting is about all that is done for groundhogs. And if I don't see any for a while I get up and move to a different field (if there's one to move to). A good bipod could help you out with your hold, that and a lot of proper practice. I've been shooting 3 and 4 position smallbore rifle competitions for over 15 years, not to mention weekly practice, and I still find it handy to use some shooting sticks for the long shots. It's better to use them and get a good hit. Good luck with your chuck hunting. Have fun!!