I'm sure you are aware that velocity typically varies from one barrel to another, even when the barrels are the same length. So the the best we can do is to make an educated guesstimation. If I cut a 26" barrel down to 22", I would expect my velocity loss to be in the range between 90 to 120 fps with a cartridge like the .280.
Over the last 40 years I have heard many rules of thumb about velocity loss per inch of barrel, and I have read at least 8 or 10 test reports where a barrel was progressively shortened to measure the velocity loss. 20 fps per inch overall seems a bit optimistic. Reducing barrel length from 26" to 24" might result in a loss of 40 to 50 fps. Reducing the length from 24" to 22" could typically result in a 50 to 60 fps loss. So I think a predicted loss of 100 fps for the shorter barrel is reasonable.
Thus it seems reasonable to guess that the velocity of the test barrel used in the loading manual might be around 3050 fps if that particular barrel were shortened to 22".
But your barrel could easily vary by plus or minus 50 to 60 fps from another barrel of the same length, brand, and rifling twist. So my guess is that it is reasonable to expect the velocity to be somewhere between 3000 fps and 3100 fps from a 22 inch barrel.
The trajectory of the bullet at 3000 fps will be quite close to the trajectory at 3100 fps. So entering a velocity value of 3050 into your ballistic calculator would seem to be a reasonable starting place.
But this is all hand waving, smoke and mirrors guesswork. Even if you knew the actual velocity in your rifle, the calculated trajectory could easily vary by an inch or more from the true trajectory at 200 yds. Using our guesses about the velocity in your rifle could easily result in a 1 to 2 inch difference at 200 yds between the calculated trajectory and the true trajectory.
The calculated trajectory will give you a fairly close prediction of your true trajectory in your rifle. In order to get a true picture of what is happening with your rifle, you will need to chronograph the velocity in your rifle and confirm the calculated trajectory by test firing at different ranges (100, 200, 300 yd, for example)