how does weather change affect the talon….

this afternoon i sat down to bust some migrating starlings…Needles to say i missed three perfect shots in a row….not just a few days ago i was shooten bottle caps of the tree limbs where the buggers always land ( 70 yards on the money….I could’nt figure out what was going on,,,so i pulled out the 30 yd target and i had a shot gun group again flyers, inconsistant velocities,,,crap….so i checked every thing…and no i don’t have it greased up or anything…My conclusion after an hour on tinkering…temps here dropped into the 40’s for the last 2 days and 20’s at night….i noticed the temp dropping and every time i would get it close something would shift…began to think i had a scope problem….adjusted the power wheel up and down..finally i went for broke and crank the darn thing back up to 8 with my new 50 gram hammer and all of the sudden bammm..ripping holes again so i waited 30 minutes and it continued to get colder and dark..shot another group and bam dead on again….do the valves tend to get sticky incold weather or what….. i had the gun ripping holes with cps at 900 fps on 6 last week the last shots i fired before dark where at 960 fps….i did’nt want to run the gun this high for shot count butt this means kodiaks are going to be running around 900…. i’m leting the gun warm up now think i’ll try another group in the morning before work and see what it does….any input….