Sitting in a high seat at the weekend and resisted the temptation to sort a few squirrels with my .308!

This led to me getting asked by the owners to come back to cull the place which is overrun with grey squirrels. 5,000 acres of mixed farm / woodland and within an hour of home....

I've got an old Hawke 2-7 x 32 (illuminated) on my Titan MPT .22 FAC (around 18 ft lbs). This scope has done well in the light use it's had, and it doesn't make sense to have a new scope which will be nearly as heavy as my rifle!

Any suggestions as to a better scope or just stick with what I have?
Which, TBH, isn't bad but may lose a bit at late dusk. And it was at late dusk when I was mobbed by about 10 squirrels. If the single shot MPT doesn't have enough fire power, my .177 - 17 shot Rapid is next on the try list. May well bring my S&W 15-22 with it's 25 shot mag for the longer ones if I go back to the high seat

Also, for squirrel shooting in open woodland, what range do you normally zero at? I'm set on 25 yds - with a mildot reticle.