Most of the guys around here like small and fast, .22-250s and .243s and if not small and fast then a 12 ga from a boat. I've killed more seals with a .30/06 than with anything else but I only hunt them on the sea ice in the spring. It doesn't matter where you hit them, if its not in the head, they go down the hole and you've lost them. The only exception to this is one I hit in the back from behind. The seal was facing directly away from me and I was shooting prone from about 200 yards. I was patiently waiting for him to raise his head so I could hit him in the back of the head, but he never raised his head above the line of his back. I was starting to feel the cold and realized I wouldn't be able to make a good shot once I started to shiver, so I aimed for the center of his back in line with his chest, the idea being that the bullet would cut his spine and penetrate into his chest. I was shooting my M-17 .30/06 and I had loaded Speer 130 gr hollow points which had proven to be very fast and very accurate from this rifle, and compared to the small bores I thought would be a great choice. As it turned out, the bullet blew up on the spine too far back and didn't penetrate into the chest. The seal immediately went down his hole and I thought it was gone, then it came back up because it couldn't swim. It took several rounds to put the poor thing away because those miserable bullets weren't penetrating. Not really the bullets fault, just the pin head who chose to use them in the wrong application. When we cut the seal up you could see fist sized cavities flecked with bullet metal where the bullet had exploded and pulverized the bone but went no further. A neck shot had finished it. This is the incident that taught me the importance of choosing the correct bullet for the job, and that speed and accuracy alone isn't enough.