The CTG is "cartridge", as part of the caliber stamped on the barrel. It's not a model designation.
The .38 S&W Special means it's chambered for exactly that, which includes all bullet weights commercially offered.
It's pressures, not bullet weights, that you need to be concerned with.
Avoid +P loads, as Sevens says, and I'd agree on limiting it to lead to prolong barrel rifling life.