Tamping for perfect shot, how far down?

[UFGators]

I noticed that my Reg Barber tamper does not go all of the way down to bottom of my empty spaz double basket. Using CCC toscano I can only get a good tamp using 17-18 grams of coffee because once the tamper clears the ridge it stops at the top of the tamper. Is this normal? Using 18 grams I can get a good tamp but this doesnt allow me to downdose if I so choose. Is this a tamper problem or coffee problem? My coffee is approaching the 3rd week since it was roasted so I suspect this is part of the problem.

[JohnB]

I checked my Coffeelab tamper in several of my empty baskets & the tamper stops with the upper edge aligned with the ridge. I've had no problems tamping 13-14g doses & up.