RE: Narrowed Down
I believe the rifle with the 1:32 twist your refering to is the Great Plains Hunter. Then answer is, sure you can shoot roundball out of it, you may not get great accuracy, but you can shoot them. That twist was made to shoot conicals and even sabots. The Great Plains Rifle on the other hand with the 1:60 twist is a roundball rifle.
Cabela's traditional Hawkins is another investment arms product, the same as Lyman. They are made in Italy for the most part. In fact the Hawkins you will notice is very similar to the Lyman Trade Rifle. The twist is the same and the apperance is the same. Just that you do not get the Lyman name. They have a 1:48 twist which will shoot both roundball and conical. It will probably shoot the powerbelts as well. Many people shoot sabots also out of the 1:48 twist. They claim to get good accuracy also. I have seen some impressive targets for people that own Lyman Trade Rifles. I see no reason why the Cabela's Hawkins would not do the same thing.
The CVA Hawkins is one of their bread and butter rifles. They have been around for ever. Many of us started out on just such a rifle. They are 1:48 twist and will do the same as the Cabela's Hawkins. They are less money, and CVA does stand behind their products. Many people claim they are great shooters.
One note, if you pick a traditional style rifle, you might want to get the biggest caliber you can get. Since you will be shooting conicals, you might as well throw a lot of lead into them. If your shooting roundball the .54 caliber has a definate knock down advantage over the .50 in the roundball department. Of course shot placement is the key to all of this.
One other point is, if you were to pick say a .54 caliber Great Plains Hunter and shoot powerbelts (I hope they will shoot good out of there... I think the Great Plains Conical might shoot better), you can always later on get a barrel in the 1-60 twist to replace that one, and shoot roundball for pleasure....
Good luck with your selection. And yes, Thompson Center makes a fine rifle also. I own enough of them to prove that point...