I just saw a 'live' CPA Benchrest (.32-20) last week.  It got me thinking about one for myself.  I've read through the posts on this forum, and my eyes began rolling back in my head.  I do have a couple of simple questions.  These will apply to the CPA rifle:   
-easiest to get reloading components for 
-dies & bullet mold
-caliber (.32-20, .32 Miller, etc)
-scopes most commonly used
Thanks.

Scope is dependent on what class you wish to shoot as the rules for each class is quite different. For Traditional Class the Lyman SuperTarget Spots and Unert 11/2 scopes in 20X are probably the most common. Non Traditional class Weaver T36, Leupold Comp. 36 or 42X, NF 12-42 BR, March 60X etc. depending on available funds.
Bullet moulds for the 32's are the most common as long as the barrel does not have a .319 groove diameter so ask before building the rifle. A .320-.321 groove is what you should be looking for to fit most available moulds either new or used. 
Dies are really not needed if shooting one case breech seated in 33-47 or 32-40. 
If you plan to shoot any fixed ammunition then the 32-40 dies are probably the easiest to come by and very inexpensive from Lyman. 
I have never seen anyone try to shoot fixed in the 32 Miller and or CPA 32-20 so I am not sure about it even being a possibility?

JLouis

If you are just starting off I would recommend the 38-55. You can purchase cast & lubed bullets from several vendors and brass is readily available and needs only a modicum of prepping. A very accurate cartridge and plenty of load data. You can use the 38-55 to shoot out to 600yd should the mood strike, and is an accurate and reasonable BP cartridge if you want to shoot in those competitions some day. 

And, as mentioned above, should you decide you want to try another cartridge (32-40, etc.) you can always have another barrel made. CPA is a great rifle for that. Start with something easy to load & shoot and then decide if you want something that takes additional effort (brass prep, etc.).

You might also want to check out the Cast Bullet Association web site. If you go to the Scores posted there will also be an equipment list posted, cartridge, load, bullet lube etc. and look what the winners are using. There have been three from my local club The Modesto Rifle Club that are National Champions in the Plainbase Class and all were using the 32-40 myself included in 2006. At last years National Championship in Raton NM one of our group who has since moved to NM took the Grand National Champion Ship honors with his 32-40 beating out the Heavy Class, Production Class & Rail Gun competitors with his 32-40 in the Plainbase Class.
Two out of the three from Modesto were using a CPA and the odd man out was using a Model J FBW,s. and has won it twice maybe three times I simply just can't remember?

I would also not use anything less than a 20 Power Scope in CBA, ISSA or ASSRA for 200yd. Benchrest shooting, in the Offhand events less power might be helpful but I have always used the same power used on the Bench.

JLouis

BP Jack is correct, come on up 

My first SS was a 38-55 for fixed ammo.  I didn't have a gun that was competitive for schuetzen or BP.  Things have changed a little in the last 30 years with faster twists and heavier bullets, but I'd still go with 32 if my primary focus was schuetzen or 40 or 45 for BP.  Those biger calibers are easier to get started with good accuracy.

I have a couple of simple questions, these will apply to the CPA rifle:  
- easiest to get reloading components for; .32-20 brass from Starline is currently in production; the ammo companies are not making the .32-40; and forming brass is a pain. The case is 90% - 95% of the case capacity of the .32 Miller Short 
- dies & bullet mold: The Hoch 207 grain base-pour mold from CPA is a good start.
- caliber (.32-20, .32 Miller, etc.): .32-20, spend your time practicing rather than forming brass. You can get .32-20 brass today and getting brass may be a problem for other calibers for several years.
- scopes most commonly used: The beauty of the CPA is you can use an external adjustment scope for Traditional Class and a internal adjustment scope for other ASSRA, CBA and ISSA matches. 

Three other thoughts: 
1, - You can easily add barrels, the .25-20 WCF and .218 Bee have the same extractor as the .32-20
2. - Gail at CPA is easy to work with and knows this shooting game. 
3. - If you want a bigger cartridge like the .32-40 later, this barrel can always be recut to the larger chamber..

For somebody who is just starting I would go with a 32-40 on a Douglas 1:14” twist barrel. Stocks are depending on what you want to do; if it is an all around gun stock it as a #52 or #49 if all you want to do is bench rest get the bench stock but pay the extra money for a through rod. Ask Paul what mold you should get and buy what he recommends it will fit correctly. 
There is lots of load information for 32-40s and when you learn how to load, cast, hold, and read the wind you can shoot with anybody with that rig. After you learn your craft you can send it back to Paul and buy a second barrel made up the way you think it should be.

40 Rod

I agree with 40 Rod too.  The point of what I [posted was to either get a BS target rifle or a fixed ammo BP rifle, not try to do a combo that is not really suited or competitive for either.   That will lead to nothing but frustration and regret. My regrettable rifle hasn't seen much use over the years