keith44spl:

Rechambering your .38-44 Heavy Duty from .38 Special to .357 Magnum MAY have been done officially or unofficially at the Smith & Wesson plant. If you get a factory letter for your revolver, it would't hurt to ask whether the observed chamber alteration had been recorded as having been done in house.

I write this because a deceased friend, while on one of his tours of the Smith & Wesson works, paused to chat with one of the gunsmiths as he worked at his bench. The gunsmith noticed that Bob was carrying a Heavy Duty and asked if he could examine it. After Bob handed him the revolver, the gunsmith inspected it quickly and carefully and then looked up its serial number. The gunsmith asked Bob whether he'd like his Heavy Duty rechambered to .357 Magnum right then and there. Bob said OK and the job was quickly and properly done.

Bob was a pistolsmith at the Rock Island Arsenal. Among other things that he did while working at the arsenal, Bob helped to develop the M-1911-based General Officer's Pistol that the Army started to issue after its supply of Colt .32 ACP and .380 ACP pistols had been exhausted.

Bob went to the Smith & Wesson works multiple times for training in his capacity as a federal employee. After he retired from the arsenal, he returned for training several more times because he was the armorer for the Scott County (Iowa) Sheriff's Department.

Bob was a great guy. I still miss him.