As near as I can tell, these are a copy of Tannerite, also nicknamed "Billy Bangers". I haven't used the brand you posted so I can't speak for their quality, but I know the guy who invented Tannerite, the original "reactive target" and I've used plenty of those. Tannerite works as advertised. I don't know how well this stuff in your link works. I've seen some imitators that work well, others don't.
To be safe, follow all directions on the website/package. Really. This is a high explosive. It can be safe if used as directed, but can be hazardous if you deviate from those parameters.
As I recall, detonation velocity is around 19,000-20,000 feet per second, but can vary: the bigger the shock it receives, the bigger the bang. So if you shoot it with a 50bmg it will be louder than if you shoot it with a 308. It can also be set off with a blasting cap and is sometimes used as an alternative to commercial blasting agents since it's a binary explosive and there are no restrictive transporting or storage requirements.
http://www.tannerite.com/