My friend has a 257 Roberts built on a Mauser 98k action. The barrel is stepped down a few steps, goes to taper, and then goes up in diameter again near the muzzle for a couple inches.

The marking on the barrel is Johnson-Gartman and then 257R. Does anyone know anything about this maker?

It may be an old Johnson Automatics barrel. They were in Rhode Island if I remember correctly. Sounds like a late 50s or early 60s job with that enlarged node on the muzzle end. That was supposed to help stabilize a lightweight barrel.

Googling Johnson-Gartman turned up some info. Here is a link to Cornell Publications which apparently has an old catalog:

Old J-G Catalog

I remember a "Johnson-Gartmen Custom Guns". But don't recall the context of the trademark. Don't know if the outfit was affiliated in any way with Melvin M. Johnson of Johnson Automatics fame.

Thanks to all so far. That little gun is one sexy little gun! Birdseye maple stock with walnut grip and forend caps. The contours on the barrel really took a craftsman. The barrel beyond the steps and before the bulb on the end is probably 7/16". The bulb on the end is approx 5/8". Very nice single stage trigger but not sure whose, looks like a European style, gracefully curved and rounded. Buehler safety, Buehler one piece base. Someone must have robbed the original guard because it has an un-modified stamped K98 guard that does not match the rest of the gun at all.