Well i am guessing this was a suicidal groundhog. I was doing some target shooting this morning and as soon as i get done out walks this groundhog about 80 yards away. I thought it was almost too good to be true. Having shot all the ammo for my 25-06 at the target i pulled out my Remington VLS 308 shooting the 175g SMK at 2860 fps. Well as you can see the SMK won the battle.
I had about the same thing happen a couple times. Once I was making sure my 25-06 was ready to go for my up and coming deer hunt. I was shooting off a bench at 200 yards and all of a sudden this ground hog just walks right out about 3 feet from my target. BIG MISTAKE. 117 Sierra at 3000 fps muzzle velocity to the head = NO HEAD TO BE FOUND.
Another time I was shooting some of my military rifles and about 75 yards away this ground hog just strolls across the range in front of me. BIG MISTAKE. I was shooting my Ishapor Enfield 7.62X51 NATO with 150 gr Sierra Match Kings. The results look a whole lot like your 175 Match Kings results.
Talk about suicidal. I once had a suicidal deer show up. I had gotten in my shooting house before day light and got set up on a old logging road that runs between two cut-overs. I put my rifle up on the 2 X 8 shooting rail and had it balanced by the forearm so all I had to do was look through the scope and I could see all the way down the road. It had just gotten light enough to see and I was looking through the scope. This 8 point buck walks broadside out into the road at a little over 100 yards and when he stops the cross hairs are perfectly lined up and centered on his front shoulder. All I did was flick the safety off and squeeze the trigger of my 25-06 and that 117 Sierra hammered him in his tracks.