I shot IHMSA for 40 years, since the beginning. The basic competitive handgun would be a .44 Super Blackhawk and 10" barrel if you're looking a revolver class. Production single-shot starts with the T-C's chambered in 7MM TCU. The Freedom Arms are top of the line in revolver, ........ I have 3 in big bore and one for .22 smallbore silhouette, plus an Anshutz pistol also for smallbore. All are capable of 40X40's when the shooter is doing his job!
It's a great challenging game and addictive, lots of practice and spare time reloading. Nothing greater than hitting rams at 200 yards/meters first time out. Try to find an experienced coach to get you going, ... there's lots of tricks.
Good luck, and press your club to try a shoot, even if it's on paper.
PM if you have more questions.