I have a Benjamin Mayhem air rifle in .22 caliber. I had noticed that I wasn't hitting where I thought the rifle was sighted in for when shooting afield. Yesterday, I took the air rifle to the indoor range to verify the zero at 25 yards. I used H&N pellets because I found the cheap Crossman, Daisy, etc. wouldn't group well at all. Yesterday, I shot at a "sight in target" with 1" squares. I found out that pellet weight has a significant affect on impact. The pellet I had been using was the H&N Terminator which weighs 16.36 grains. I compared the impact of it with a new to me pellet, the H&N Hornet, which has weight of 16.20 grains. The heavier H&N Terminator pellet shot consistently higher than the H&N Hornet. In fact, it shot 2 1/2 inches higher. If I remember correctly, this is opposite what I should expect from a cartridge rifle, but about the same as what I expect from cartridge fired handguns. It was also very surprising that a .16 grain difference in weight made that much of a difference. Of course, I've also learned that, at least with my Benjamin Mayhem, that a "light hold" makes for better accuracy, compared to a "spot weld" hold for a cartridge fired rifle. BTW, I was shooting my air rifle "off hand", not from a rest. I was relieved to learn that there wasn't a problem with my scope, rifle or marksmanship. I did learn that it doesn't pay to be lazy and guess about zero.