Interesting concept using cloth. I suspect a soft .430" short bullet might be made to fit a .45 RB rifle barrel using this method. As well, a pure lead .452" short bullet might fit a .50.
If you keep them really short, they will fly better. Such as 165 to 200gr. in the .430" and 185 to 220gr. in the .452" bullets. Regardless of the bore you are putting them through, they will still be a .44 or .45 bullet launched from a slow twist. Winchester did this after the ML era, but his guns were NEVER famous for accuracy, and that was with .56 to 60" twists in .45 and .50's, seems to me.
In thinking more of this concept, it is similar to the picket bullets. Thus, short and a gas-check design might fold the cloth more easily. A rod end that fits the bullet nose and is tight to the bore will centre them better. The bug bugaboo with picket bullets, is getting started them straight into the bore, then keeping them straight all the way down. A guide bullet starter will be a help, but then so will a proper rod tip that fits the bullet. Epoxy can be cast using seran-wrap around a bullet's nose to make the perfect cavity in a form fitting rod tip. The larger flared shotgun and smoothbore tips from Track would be a good place to get one. You can also make wide rod tips from ctg. brass - at least up to 50 using standard mag. brass, .54 with Ultra brass, .10 bore using .5's and .100 using 20 mm brass.
Good enough accuracy for deer at close range, but then a R.E.A.L. bullet from Lee lubed with Lyman's BP Gold, SPG or 60/40 Beeswax/Vaseline would likely be better than cloth patched pistol bullets.