RE: Trajectory - powerbeltbullets
A real misconception of the 1:48 twist is that they will not stabalize a sabot or powerbelt. That is not the case at all. Many 1:48 twist barrels are excellent sabot and powerbelt shooters. A lot of it is determined by the depth of rifling in the barrel. The PA Pellet .50 caliber flintlock was designed for just that purpose. It was made to shoot sabots and the bigger conicals such as powerbelts, with great accuracy. Yet because of the rifling it will not shoot roundball all that well. This is what I have learned from all my research on the rifle.
This is also the reason why some of the 1:48 twist rifles are outstanding roundball shooters and they do not shoot conicals or sabots very well at all. Again, it is in the design of the barrel. Many people manufacture the 1:48 twist so it will do a good job with both roundball and conical bullets. This is the case but if you truely question their owner, they will admit that it does shoot one much better then the other.
The Thompson Center New Englander for example. My friend's .50 caliber with 1:48 twist is an outstanding conical and sabot shooter. Roundball on the other hand are a lost cause with the rifle. My Renegade is just the opposite, a great roundball rifle but will not shoot sabots. Again, the design of the barrel.
As for plastic buildup in a barrel, as long as you clean your rifle with a quality gun solvent that is made to remove plastic, lead, and copper deposits and use a brass bore brush with that solvent, the buildup will not really happen.