Pretty straight-forward question. For a civilian (One who knows guns and gunshop owners well), how hard was it to obtain a reasonable amount of these rounds? How expensive?
Hi OP, can you clarify, do you mean the 1980s, and in which jurisdiction (country, state, city)? That information will greatly assist anyone considering answering here. Thanks!
I don't know about the availability of any handgun ammunition in 1980's New York because I'm not sure about their gun laws.
But the Smith & Wesson Model 29 revolver chambered in .44 Remington Magnum, (the "Dirty Harry" gun,) was introduced in 1956 according to S&W's website. As the chambering for a commercial model from one of the largest domestic gun manufacturers that had been in production for around 25 years, the ammunition is going to be generally available. I'm not sure if non gun store retailers would carry it (like K-Mart or Sears,) but most gun stores would stock ammunition from one or two manufacturers in the same way gun stores stock it today.
It wouldn't be less common than any other type of ammunition.
I'm not as familiar with the .41 Remington Magnum, so I can't say about that.