I and my hunting buddy did use the Old Style Grand Slam. The one with the really hard lead in the bottom half of the bullet where the jacket was pretty thick but the front part of the bullet had soft lead and a thinner jacket. We were both using them in 25-06s for BIG body white tail deer. My buddy was given a hunt as a Christmas gift by his boss on a big farm in Alabama that had HUGE deer on it. They recommended that you bring at least a 7mm mag. My buddy is a retired Marine and can shoot the eye out of a gnat at 500 yards
. He took his trusty custom Rem 700 with a Heart barrel in 25-06 that he had been using to bean field hunt in east NC. He worked up a load with H-4831 and used the 120 gr Speer Grand Slam. He killed two Huge bucks on that hunt and one doe that was a requirement to shoot before you could take a buck. All one shot through the shoulders and dropped in their tracks dead and the bullet exited with about a quarter size hole. I decided to try the Grand Slam on a few deer and they would shoot through them from almost any direction. I did recover one bullet. I shot a good size buck at only 50 yards in the chest as he faced me. He fell back on his butt rolled over and was dead. I found the bullet when cutting up the meat. It was just under the hide of the right ham after it had passed completely through that buck and smashed through the ball socket of that ham. It was a text book mushroom and weight was 87 grs. Muzzle velocity was 3000 fps at muzzle so it still had to be going at least 2900 on impact. They have changed the Grand Slam in the past years. My understanding is that it is just a Hot Core bullet with a pretty thick back half of the jacket. The ones I and my buddy used were very accurate though.