Huge difference between spring BA and gas BA, spring BA will almost always put out the same velocity regardless of temperature (will change only due to air density due to temp), but if you actually get a gas rifle to shoot at 450fps one day, the next it could drop to 400fps, the day after it could shoot over 500fps. Considering the amount of time it takes to rip the bolt open to adjust, reassemble, chrony............. it might take you an hour to get it shooting under the field limits.
One thing about that rifle, a couple of us had one on the team (I still have mine), it'll punch through both sides of a pop can at 100ft on a hot day, and I was also able to make it blow holes in the bottom of a tuna can at 30ft (my 500fps M24 at the time would just leave deep dents using 0.36g). Which adds another topic, fill it full of propane, you need to purge the pressure by dry firing a few times. When I first got mine, I tested it a couple days later in the basement (was about +34C outside), my first shot after filling was around 715fps, second was 620fps, third was 560fps, the rest for 20 shots was between 550-560fps. With duster, almost same reaction, just 100fps lower on all velocities.