The feeding issue with the earlier Models 39 and 59 was related to the feed ramp, not the magazines. The ramp on the early 39-2 and 59 had a double-angle that resulted in a hump in the ramp. This was revised by S&W to a straight ramp and the feed ramp was to be changed to a straight ramp. This was accomplished in the field by grinding the hump out of the ramp.
A 3/8" cylindrical grinding point in a Dremel tool was used to accomplish this. The ramp was then polished using a 3/8" Cratex polishing point in the Dremel.
It took me weeks to get all our departments guns in from the field and correct the feed ramp on the several hundred guns we had.
Note that this was a change done in the field at the direction of S&W. This was in 1973.