Boy are YOU gonna have fun!
In Highpower AND Smallbore!
My recommendation (as someone who does the same thing.. train for Highpower with Smallbore) is this;
Get your Club or State Association to provide you with an AR-15 Service Rifle, and then get a Compass Lake (or other reputable builder) AR- Service Rifle type "Dedicated .22lr Upper Assembly".
That is the BEST way to go! You'll be training with the SAME sights, SAME trigger, and SAME weight and feel (and SAME sling, glove, hold, sight picture, etc) as you will be competing with.
Otherwise, a good used Anschutz or other smallbore rifle will be perfectly adequate for 100 yard training! In fact, I'm not very familliar with the BRNO #4, but it SHOULD be just fine at 100 yards also!
Being as how you're on the State Team, I figure you're not a Marksman class shooter, so I haven't recommended something like the Mossberg M44 .22 Training rifle that the CMP was selling (they're out now, but you can find them second hand for $200 or less).. You would quickly out-strip the Mossbergs capabilities if you shoot Expert Class or better.
You migh, however, consider the Kimber M82 Government rifles available from CMP. At $600, thought they are FINE rifles, they're not really ideal training rifles. Their stock is not really optimal, and their accuracy potential is less than that of a good used Anschutz 54 for about the same money.
Like I said, if you are ONLY training for Highpower (particularly Service Rifle as opposed to Match Rifle) then the BEST option is a GOOD .22LR AR upper on an AR Service Rifle lower. I know it's a bloody lot of money... and as a junior, dollars can be short... but if you are serious about being a serious competitor, I honestly don't think there is ANY better investment than a Compass Lake Engineering (or Accuracy Speaks, or other reputable maker) Rimfire Upper. And I don't think there is any better Service Rifle than the AR (I shot the M1A for 12 years before switching to the AR, and love the M1A, but will never shoot it again in competition!)..
I hope this helps!
Paul F.