Yeah, there's around 1000 fps difference. Exactly how much depends on the loads--in my CZ 452 the A17 ammo, for the Savage autoloader, gets around 2800 fps, with the same 17-grain bullets as the standard HMR ammo. My handloads in the .17 Hornet get around 3800, but with the 20-grain V-Max, which holds on to velocity better than the 17-grain bullets in the HMR.
In general I'd say there's at least 100 yards difference in consistent performance, maybe more like 150. The longest shot I've seen anybody make with the .17 HMR was 303 yards--and the guy was one of my friends who'd never fired one before. His very first shot, before he had a clue about the trajectory, hit a prairie dog in the head. Generally around 250 is stretching it on PD's, usually requiring more than one shot to hit 'em, and 150-200 is better for consistent hits, exactly how far depending on the wind.
The HMR isn't as loud as the Hornet, but I still wear ear protection. That said, I shoot my .17 HMR a lot when starting out on a PD town, because the report doesn't scare them into their holes nearly as quickly as a centerfire, whether a .17 Hornet or .223. After the PDs in rimfire range are dead or down their holes, then the bigger rounds come out.
It's a great gopher round.
