I've tried 5 different lots of center x, 2 lots of midas plus, 2 lots of SK rifle match, SK long range match, 2 lots of Polar Biathlon, eley club and eley tenex. The factory barrel shot the center X and Midas plus well and I won a bulls eye shootout with Lapua Polar Biathlon (497 score out of a possible 500).Here's a suggestion. Keep in mind that it's not the brand or name on the box that any barrel "likes".
The fact is that barrels don't know what brand or variety of ammo is being used, least of all whether it's Lapua X-Act, Midas, or Center X. Except for the packaging, these three are indistinguishable from each other.
What rifles shoot well is good quality and consistent ammo, regardless of the name. Look for good lot of Center X. It's not necessary for you to spend X-Act money.
The KI barrel shoots the X-Act fairly well and nothing else shoots good enough to complete with the guys I'm shooting against. Again, the factory barrel shot most Lapua ammo pretty well and I would usually win 3+ rounds. The KI barrel is all over the place.
I only changed barrels, nothing else.
Trying to troubleshoot, I double checked the torque on the screws and made sure they were not bottoming out...
The barrel is threaded, and have tried a silencer, it seems to help tighten the groups somewhat, but nothing to write home about.
This week I'm going to clean the barrel again with the IOSSO bore paste and give the Tenex another try. Also going to try a friend's lot of Polar Biathlon that his KI barrel shoots very well.
Just thinking I got a bad barrel. I know it happens.