I once owned a 22 pound H. V. PERRY rifle with a Fredonia, New York, address. It included a hand dovetailed walnut box, with hinged lid, containing the false-muzzle, guide bullet starter, mold, and swage. Ned Roberts considered Perry one of the great target rifle makers. He was born in about 1828, was working in Dansville, New York, in 1850: Fredonia, New York, 1852-1865; and in Jamestown, New York, 1865-1897. People either like or hate the architecture of these "fishbelly" rifles, but if you have ever put one to your shoulder, you will be pleasantly surprised at how nicely they hold. Personally, I find them oddly attractive, some more than others, as there are several variations within this style of architecture.
Remington did indeed supply barrels to the trade for a long number of years, but these were primarily cast steel barrel blanks, not finished barrels. They were not normally rifled, or even reamed to the finished bore size. I am skeptical about them being supplied by Remington (or any of the other suppliers) with the muzzle already turned for a guide bullet starter. If that were the case, one would expect some degree of standardization, and that is far from the case. I currently own no less than 47 rifles that have muzzles turned for a starter. The dimensions are all over the map, both in diameter and in the length of the turned section. There is no interchangeability among them. Not to mention other little details such as the knurled band on the muzzle of this one, which are quite individual. It stands to reason that if a gunsmith had a lathe with which to make the guide bullet starter, he also had the capability of turning the muzzle to accept the guide bullet starter.