Head shots are sometimes the only shot you have. Like the shot I made behind the ear. If I had tried to make a heart lung shot the bullet would have exploded just under the hide. The Moose would have walked away with just a minor flesh wound. By putting it behind the right ear it exploded in the brain cavity. Remember I was using Speer TNTs. Bullets desitgned for varmints not big game.
Now for the Kid Dand knows the head shot was the best shot for him as well. A 30-30 to the heart lungs means the Moose can go for a long walk. Moose are not hard to kill, they just don't die fast. If there is any water close by they will head for it. If it's a river you will lose them when they dive in and start swimming. That's when they will die, and down river they go. If you don't drop them on the spot, they will go to the most inaccessiable spot they can find before dying. Then you have 800 to 1200 lbs of meat to transport back to camp, to the boat, or to somewhere you can get it to an area where you can reach it with a vehicle.
Heart Lung shot is not the shot to take with a moose. I speak from 40 years experience hunting the biggest Moose in North America. If you are hunting in my camp you will make a center of the shoulder shot, or you will never be invited back. Center of the shoulder shot will brake both shoulders and drop a Moose on the spot. The problem with that is a 30-30 does not have enough energy to brake the shoulder. Oh it may damage one shoulder, but not enough the Moose can not get around and move off or to water. It takes a .338 Win Mag or something in that range to brake both shoulders. A couple of years ago a guy in our camp thought his gun was big enough to not have to worry about the Center of the shoulder shot. He was shooting a .375 H&H Mag. He made the heart lung shot. The medium sized Bull ran about 75 yards up a steep slope, turned around and ran back down, jumping into the river. The shooter jumped into a canoe and gave chase. My partner and I fixed breakfast, broke camp, loaded the rafts and followed. three miles later we found them. Sitting on a gravel bar in the middle of the river, in two feet of water. We pushed it on over the gravel bar and guided it down stream to an area where we could get it close to shore. that was one of the most miserable mornings I have ever spent. Standing in two feet of water dressing out a Moose. You just don't drag 1,000 lbs of dead weight up to a dry shore. River water never gets above 37 degrees.
Now if you are hunting in the late winter like Dand was, yea there is no water there, it's all frozen. And if the Moose runs, so what just follow it with the snowmachines till it goes down. A heart lung shot will work there.