.22 bolt action CZ 455, grouping went from 1/2 at 50 yards to 1-2 inches

[axis007]

Shooting Bench-rest precision style in my backyard, using a CZ 455, American Rimfire Target, first 25 shots grouping 1/2 inch, at 50 yards, CCI Subsonic at 1050fps next 20-50 shots missing by 1-2 inches? cannot figure out why, Fatigue? unlikely. the Barrel does not feel warm or hot, cannot figure out why? any suggestions or comments?

 

[swampbuck]

Rimfire accuracy is all about the ammo. An heat probably is playing a role. Along with human focus and stamina. Give it a rest and start a new.

 

[Turkeytider]

Obviously can’t know for sure with your gun, but I’ve decided my 17HMR shoots more accurately early on in a range session when it’s clean(er) than towards the end of a 50 round box. Left it fouled as a test and accuracy was not as good early in the next session.

 

[Chris1972]

Even though it’s the same ammo did you change boxes during that time? Different lot numbers can do that to you.