Back in the day, the individual parks had a cache of weapons, and you were issued same upon arrival at your current post. In those days, revolvers ruled, typically S&W K-frames. Ammo was the .38 +P+ 110 JHP Treasury load.
First post-Smith Model 15
second-" Model 10
third- " M66
fourth- L-frame, 686 (stainless) and the first issue of 125 mag ammo
Lo and behold, we made the jump to auto pistol. Everybody got a Sig P228 with 147gr JHP ammo initially. A central cache/issue system began at the academy, circa 1995 +/-. As the auto pistol transition progressed, field staff and new staff began to receive the option for a "one time" choice between Sig P220-.45, P226-9mm (and now .40 cal) or P229-.40) A few of the early P228's are still out there, there users preferring not to transition, as well as a smattering of P225 single stack 9mm's for small handed staff. The "one time" issue has been flexible and I've know several rangers who have changed models and caliber mid career. (still Sig as listed above)