Different guns like different diets. I found this to be extremely true while shooting competitively many years ago. I had 1911s that had been rebuilt by by Jim Clark, one gun was a tack driver with Winchester match grade ammo, but was a very poor performer with anything else. Over a period of several years I worked up many different hand-loads, and still could not get the accuracy I had with the Winchester ammo.
But by the same token, just last week I took a 6.5x55 Swed to the range to sight it in. The gun has been fully sportrized, with a 3-9 Leopold scope added. I started shooting with Remington factory 140gr ammo. I had it grouping very tight about two inches above the bull with that ammo. After firing all of my ammo, my son gave me a box of S&B 139gs SP ammo. It was all over the target. I then switched to some of his hand loads with a 120gr Nosler ballistic point, they grouped tight just above the Remington. Could it be that the quality control of the S&B is such that it will not give good performance, or does the gun not like that ammo?
The point. After many years of experience, I am convinced that a load had to be worked up, or found for each firearm, and all ammo of a certain type will not provide the same degree of accuracy in like guns.
