Joe - I have never been able to discover any difference between the red sabots and the blue sabots. The Blue Sabots seem to be the latest production. I suspect that all the early “tan” sabots were red, and are simply faded, but I could be wrong. That is if we are still talking these Peters-headstamped loads.
As to the cannelures, there are several patterns. The earliest loading seems to be the one with a single, smooth cannelure. What I feel is the next variation has two cannelures, both smooth.
The top cannelure is 4.95 mm below the case mouth, with the second one about 3.45 mm below the first one. These measurements and all others to follow are VERY approximate. My old eyes find it difficult to locate the center of these cannelures for measurements. The next one has the top cannelure about .410 mm from the case mouth and the two cannelures about .315-.320 mm apart. Both cannelures are smooth. Finally, there are a group with the top cannelure about .470 mm below the case mouth with the second cannelure about the same distance below the first cannelure. These have a knurled bottom cannelure and a smooth top cannelure, and are found with red sabot in brass and nickeled cases, and with blue sabot in nickeled cases only.
I have not addressed the Evansville Chrysler rounds or the Remington Arms (R A) rounds here, only the civilian ones. The civilian shot cartridges seem to have been made by Peters until about 1951. I have a 1950 catalog that shows them, and a 1952 catalog that does not. So, that’s as close as I can come. I believe they were introduced in the early 1920s. I have no early Peters catalogs from this era, but the book “Thompson: The American Legend,” by Tracie L. Hill, indicates that the special shot magazine for the Thompson SMG was first patented August 24, 1920. At least prototype cartridges would have had to be available for establishing the internal dimensions of the magazine. Due to Sabot crushing, the capacity of the magazine, initially twenty rounds, was changed to eighteen rounds in very early 1921. The same magazine was used a little later with the long .45 Remington-Thompson ball cartridge. (Pages 346,383-385.)
Edited to correct type of measurements taken - originally and erroneously shown as inch measurements when in truth they were metric.