In HFT your scope choice isn't quite as limited as it is in FT, so pretty much any scope will do for HFT.
The important thing to remember with HFT is that you can't adjust your scope during the course, so target turrets aren't going to be important, adjustable parallax isn't needed and scopes with a magnification greater than about 12x aren't going to be much use to you.
Go for something with about a 40mm objective lens. The smaller the objective lens, the greater the depth of field - generally) so smaller is better in terms of depth of field, but the trade off is that if you have a smaller objective that will limit the amount of light coming into the scope, so you may have to invest in more expensive lenses and coatings to compensate.
If you're just going to try HFT, I would recommend buying something 2nd hand and don't spend a huge amount of money.
There's a Bushnell Elite 10x42 for sale at the moment on this forum, they're not a bad scope for HFT.