I totally agree with the prior post. If the shots are flying up up and away, it is definitely not the ammunition.
I had a similar experience with my brother. He bought a brand new Handi-Rifle in .30-06. He never kills game past 100 yards, so to sight in, he always starts at 50 yards. He complained to me that shooting from the bench, his rifle would put two rounds very close to each other at 50 yards (often touching), but that after that, the shots starting going up up and away with every subsequent shot, until they were hitting as high as 6 inches high at 50 yards.
I went down to his farm, and watched him shoot, and the rifle performed exactly as he said. I then took the rifle from him. Waited 15 minutes, and started over.
I fired the first shot, and waited 3 minutes. He said, "What in the world are you doing?" I said, "I'm letting the barrel cool. Ever heard of it?"
After 3 minutes, I fired the second shot. It touched the first shot.
I waited another 3 minutes, and fired a third shot. It was within 1/8th of an inch of the second shot. I waited another 3 minutes and fired, waited another three minutes and fired, waiting another 3 minutes and fired.
In the end, I had six holes, 5 of which were touching each other.
I then told him, "The 30-06 is a high pressure, high power cartridge, that generates alot of heat. You can't shoot it as if you were cycling .38 special loads thru a .357 lever action carbine, or it will never group. This is generally true of all modern big game rounds, and most of the ultra fast varmint rounds."
Hope this helps.
Mannyrock