Hey Jason, my non-tuned Viper was getting groups like that at 8 meter distances with Crosman Hunting (Cheap ones in a small milk carton) also. After a little over 1200 shots, she didn't like the hunting pellets that much anymore....and liked the Crosman Premier Hollow Points. So I shot those outta her. But then I started to shoot some GTA Shooting Matches....and the Viper is one of my more accurate airguns....so I used her for the 30 Yd Bench Rested Rifle Match (No PCP's in this match). Unfortunately, the CPHP's had flyers every 5th or 6th shot.....the Crosman Hunting pellets were abit worst. The search had begun!!!!! After testing about 8 types/brands of pellet, I finally found one that can land in the "Black" everytime if I do my part......the extra heavy .177 Beeman Kodiak (10.6 grain)....so I use them for the match. But there's a belief that heavy pellets will shorten the gun's spring.....so I go back to the Crosman Hunting and Hollow Pts. for regular plinking.
Btw, the spring did break after over 3000 shots.....don't know if it was just it's time or because of the heavy pellets. Replaced the spring with a Crosman spring....she is still shooting excellent.
