Oddly enough, the Texas Rangers weren't considered the last word in weapons selection across the length and breadth of the Old West.
You also believe that they didn't all favor the .45, when the sole mention of that appears in 'Six Years With the Texas Rangers' by Gillette, who found the recoil somewhat punishing, and was advised that the lighter-recoiling .38-40 would suit his needs, so he armed himself thusly, but that's not to say that they all did so.
They were a small, almost isolated group operating in a huge state, and they got a helluva lot of ink in later years, thanks to a good working relationship with the press, but they didn't have a 'weapons selection committee' that handed down pronouncements.
If that were the case, they'd all have ridden the same saddles and worn the same leather.
Colts were ubiquitous and cheaper, besides - as was their ammunition - their Sharps carbines were issued, while the Winchesters were cheaper when bought in multiples, and the Model 1895 was the latest in Winchester's line, firing a powerful cartridge - something desireable when there's little back-up.
Scouts Out!