Part of me says get a decent AR15 (being evil, and black, and all). Part of me says get a M1 Garand (do I really need to explain this?). What ever I get, I want to at least be able to migrate it reasonablely easily into a target grade rifle.
Are there other options for a competition rifles?
Conventional wisdom says get a National Match AR-15 from Rock River or Armalite or build your own with a Rock River NM complete lower and a custom NM upper from somebody like Compass Lake Engieering.
However, Highpower is NOT limited to military look-alike rifles prepared for match use, properly referred to in the rules as "service rifles".
You can also get into it using what is known in the rules as an NRA Match Rifle. It can be almost anything that has a 5 round magazine, can be quickly reloaded, has iron sights, and can accept a sling for support. Something like this:
I found in in Gunbroker.com for $1600. I have seen some for less in similar condition. It is a custom highpower rifle built on a Winchester Model 70 action. With a little bit of practice, the bolt action is definitely NOT a handicap in the rapids. Bolt actions actually have dominated the sport of Highpower at the highest levels. and continue to do so today.
A new NM AR-15 Service Rifle will cost you from $900 to $1300, depending on what you buy, so the cost is not all that different. If you don't reload, an AR service rifle or a bolt gun in 308 Winchester are your only realistic choices because factory loaded ammo is easily available.
Forget about the M1 and M14 (M1A) as highpower target rifles unless you are ready to sink $2000 into them over cost. Otherwise you will not have an accurate rifle. And beginners, more than anyone, need accurate rifles. You cannot progress if your weapon is spraying shots all over the target despite your best efforts.
Back two weekends ago I shot a 600 yard prone match with my M1 (in GI condition). I normally shoot 193 to 198 out of 200 points at 600 yards with my NM AR or my Model 70. Best I could manage with my M1 was a 169. And I have a Master classification in Highpower. How much fun would you have as a beginner with a rifle that can barely perform in the hands of someone who knows what he is doing? Trust me, it's frustrating. And frustration will kill your interest pretty quickly.