Suthern Buck is talking about the .17 Remington, not the .17 HMR.

The .17 Rem is a centerfire bottleneck rifle cartridge similar to, but not exactly, a necked down version of the .223 Rem (some of the dimensions other than the neck are different), so it's not at all unreasonable for it to smoke that little 25gr. bullet out there at 4,000+ fps.

The .17HMR, as you know, is a necked down .22WMR. They are the same caliber, but totally different cartridges alltogether.

Mike