Only just started in HFT and I have been using a .22 springer. I'm not winning anything with it but I've really enjoyed the challenge.
The big problem I've found with a .22 springer is the trajectory of the pellet drops pretty severely at longer ranges so your aim points are significantly different between say 40yards and 45yards. Estimate the distance wrong and you'll either sail over the top of the plate or hit below.
All that said work with what you've got and see how you get on. It is addictive and once you join a club and try out other folks rifles you'll get a better idea of what works for you.