Best pellets for norica viriatus BP HT .22 airgun

I'm not sure what you mean by long distance. That rifle is not available in the US-all I can recommend is start with JSB 18.1s or JSB Mosnters, Maybe try H&N Baracudas also. See what groups best at 25 yards first, then try 50 yards and see what happens further out. The test results will be what determine the pellet your gun prefers. You might inquire of the manufacturer if the gun is recommended for use with slugs-many long range shooters seem to find slugs perform well at longer distance as long as the gun is powerful enough to push the slugs fast enough for good accuracy.