They are a great hunting bullet. Part of the reason they penetrate just a bit less than a partition is because they actually retain a mushroom. Their penetration is still very good. They are underrated by those who dont use them, but those of us who do know they are a great bullet.

I killed one bull (5x4) with my .300 Mag and a Grand Slam at 3050 fps muzzle velocity. I was on one side of a canyon and the bull was going up the other side about 225 yards. I could tell he wasn't going to turn before he topped out, so I put the crosshairs between his shoulders and pulled the trigger. He dropped, rolled over, kicked twice, and was dead, all in about 10 seconds. However, upon examining him when caping and quartering him out, I found that the bullet had disintegrated when it hit the spine. I was picking lead flecks the size of the head of a pin from the loins for hours!! The bullet hit the spine and just totally blew up!! It barely punched a hole in the top side of the spine, and never made it out the other.Nor was the rest of the bullet inside the spine. I really wasn't happy with the way the GS stayed together, so I never used them again. I think they are a soft bullet, just a bit too fragile for my likes, at least on elk. They're probably fine for deer..

I have used them interchangably with partitions letting the accuracy of each in the chosen rifle be the deciding factor. The Grand Slams that I have are "double core" bullets. That is to say a slug of hard lead in put into the cup and then a softer slug is put ontop it. The softer lead being toward the nose of the bullet. Then the two parts are bonded together and all that neat stuff that I don't understand. The end results are a bullet that is a "partition" bullet in that the nose portion opens up readidly while the rear portion stays intact to drive thru the game.
I have not talked to Speer but I am told the Grand Slams are no longer made this way but now the core is a single unit and the jacket design controls the expansion. I don't know if this is true or not. I am also unlikely to find out as I have enough 7mm and .308 Grand Slams of varying weights to last me a couple of life times.
I have only used a couple since moving to WV and quickly decided that they weren't needed for the small bodied whitetails around here. But, if I were going elk hunting tomorrow, I'd be carrying some cartridges loaded with Grand Slams.

One of the greatest compliments ever given the Grand Slam was by a competitor.....Sierra!!!! In their advertisemant they show a marvelously mushroomed Grand Slam bullet that performed beautifully with less than MOA accuracy. Just what we're all looking for. Sierra's intent was to show that their standard Game King was just as good at half the price. They made their point.

However I've never been able to get anything better than 3" groups with them and others here have had the same experience......so a big thank you to Sierra for bolstering the accuracy reputation of the Grand slam.

There's no reason they should not be a great performer assuming their accuracy fit's your liking.....but so far that hasn't been the experience here.

I find the Speer Grand Slam to be one of the best hunting bullets made. My dad used to say (many years ago)"Sierra at the bench and Speer in the field." I think he was correct. The Grand Slam is a hard hitter and fairly accurate to boot. Best wishes.

Cal - Montreal