It would make some sense since they wore little if any armor. There would definitely have been a few situations where it would have created a possible advantage.
However....
The guns simply had better range and were easier for training purposes. While training with a pistol or rifle does take some time, I believe it is likely easier to learn with a rifle.
It takes more time to get decent, especially at long range, with a bow. Also, if the bow is going to shoot a long distance, it would take some time for the archers to build up to shooting the required weight.
I think they used guns for the same reason the indians switched to them. Quicker and better range. Possibly not in the beginning, but certainly in the end....