Deer rifle and ammunition combinations.
When a bullet exits the muzzle of a rifle, several things are happening. The gases from the ignition of the powder in the case, expand the case to form a seal against the chamber walls, and continue to expand forcing the bullet out of the case, into the throat, and rifling, which cause the bullet to spin with the rifling. It continues to spin after it exits. This stabilizes the bullet as it heads to it’s destination. The explosive force of the propellant, and the torque of the rifling, set up patterns of vibration in the barrel. When the bullet exits, it will exit at a particular point in that cycle of vibration. If the ammunition is consistent, and the operators hold is consistent, it will exit at the same point in the cycle each time it goes bang.
Good, or bad vibrations.
Different ammunition will set up different vibration patterns, and therefore produce different results. That is, the bullet will leave the muzzle at a different place. this may be only a fraction of an inch at the muzzle, but it can translate into several inches, or feet at the target end. If the barrel is vibrating upward, it will be higher, if downward, it will be lower if right or left, it will be right or left of it’s intended goal.
Try this. Take several boxes of differing ammunition for the same rifle to the range. Set up several targets, and fire five rounds each at 100 yards of each type. Some will be grouped tighter than others. If you have one that performs particularly well, you should make that one your ammunition of choice. Even if it lands low and to the left of the target, you can adjust the sights or scopes to put that group in the bullseye.
A personal experience.
I had a friend who had an old Enfield rifle that he was about ready to part with because he couldn’t keep it on the paper. He asked me to give it a try. I sat at the bench and fired five rounds of his ammo at the bullseye. None of those five rounds came within 8 inches of the bullseye, but they were all clustered in a nice little 1 inch or less cluster at the bottom right hand corner of the target. When he peered through the spotting scope at the spectacle, he changed his mind about the rifle. Damn the luck! I really wanted it for my collection!
Group size is important. Where the group lands is also important, but that is just a matter of moving the sights. A different ammunition might have put one round in the bull, and the rest in each corner. That would almost guarantee an hour of following a long blood trail through dense brush in a hunting scenario.