Two months ago I became happy owner of new Challenge HFT. Then I set the velocity at 238m/s as it gave me the best consistensy both at 50m. on paper target and at chrono test +/-0.5m/s For two months I have shot 1500 pellets/3 tins. Yesterday at the range at 50m on paper I noticed a wide spread of the group inspite of using pellets from the same batch. I checked the velocity and it was drifted up to 242m/s . I lowered it down to 238m/s and the group became as tight as it previously was. I measure the velocity always at constant environment after having the rifle tempered for some time so I do not suppose a temperature issue. My question is about the significant velocity drift after shooting just 3 tins. Is this drift normal or it is related just to the brand new rifles until they settle down? Do I need periodically to check the velocity if it will drift again and again? Drift of 3-4m/s has quite an impact on accuracy on 50 meters and can you give me advice how to keep it constant to the preset value of 238m/s for longer period - shots count? Thank you!