Once you upgrade enough to get Hammers second (close range) special that is no longer an issue. For now the fire rate tech is useless for the same reason as Colt: The stat does nothing.
It could be that Colt becomes slightly better than Hammer after that is fixed because Colts secondary effects (burning damage is better than armor piercing for the close range special that is used the most) are less awful. However that is a small difference, since dinosaur skills tend to just be better while you have a full power bar (Coelo stun jump, for example) so if you already invested a lot of Gun Tool Kits into your Hammer switchig woulkd probably do more harm than good.
Switching to Peacemaker once you unlock it is another story since that’s a long range gun and useful with a fast dinosaur (Pachy, Coelo) for kiting. However by that time your Hammer would be at level 14 already and it would waste massive amounts of GTK.