When it comes to finding accurate dates, my problem is, there are so many conflicting ranges online and in books. Source A will say one range, Source B will be close but different by a couple of years and Source C will be way off in left field. I suspect that some of the problems are some sources are giving ranges for the line and other sites are giving exact dates for a specific headstamp design.
It's like with this example. I sent Remington the two pics above because the are very similar to ones that I was asked about. The date range that I was given came directly from Remington, which technically should be accurate. Remington was very specific with the dates for these specific headstamps. Here's the problem. I know that the Nitro Club was made well into the 1940's (according to magazine ads and store displays). Now to try to figure out what order the headstamps came in and what the more recent ones look like.
Doing some other research, I also found out that there is one Winchester head that had over 400 seperate loads associated with it (both Winchester and private loads). Without knowing the load, paper color and top wad, it is impossible to date the head so it is usually given the date that Winchester factory loaded it (even though the shell was sold empty to different stores for custom or private loads for years before and after the years that Winchseter did factory loads).
Doug