I agree that the Lyman Great Plains flinters are a step above the 150 to 250 dollar guns, but they don' t come in 1:48 you get either 1:32(I think, it might even be faster) or a 1:60. Lyman does sell the Deer Stalker and Trade rifle in a Flinter with a 1:48 twist- if they use they same lock on these guns as they use on their Great Plains guns they would be excellent choices.

If buying a used gun, run a ramrond with a cleaning jag and patch down the barrel, if you feel any loose areas - don' t buy the gun, there may be small bulge in the barrel. When you remove the patch make sure it looks clean. Also look for any rust or pitting in the barrel.

Good luck