They, Pedersoli, as well as dealers, say the carbine is the same as the full sized frontier, only shorter. This is not essentially true. According to the Pedersoli website, the carbines have a 1:34 twist (which is fast enough to in some cases to stabilize a sabot round) and depending on the depth of the rifling, may also work for round ball.
The basic frontier rifle have either 1:48 and 1:65 twist rates, which will shoot some conicals well and round ball, but not sabots.
The Pedersoli frontier barrels have a habit of cutting patches if one uses patched round ball, so some home polishing of the interior of the barrel may be needed to correct this.
I have no use for a historic-looking short, long-rifle, costing $650-$680, when I can spend about $30 more and get an actual long rifle. The shorter rifle eliminates the advantage of the long sight plain that one gets with the longer barrel.
If one needs an 11" shorter barrel, and so is going to use a very short black powder rifle, and possibly hang a scope on it, it would be better to save money, and get an inline with a basic scope, than to invest in a "frontier carbine" (imho)
LD