If you search the TS.com postings you might still find a link to an old remington publication that will give you the recipe to duplicate their shells using popular powders such as red dot, american select and clays. I know it was here a month ago because I went to it.
The manager of the Remington ammunition manufacturing plant making STS shells has been on this site several times debunking the myths.
I'm citing this from memory now, so you should do a search if you ant the exact wording.
The powder with the green flakes in it is a custom formulation with a Red Dot burning speed. It is not Green Dot. It is not Red Dot with green flakes instead of red.
When Remington switched from the equivalent of International Clays in their STS Nitro loads, they used Hodgdon TightGroup, but not the exact same stuff you or I can buy. Subsequently, Remington sourced this powder from someone other than Hodgdon. This has been confirmed by Hodgdon and Remington representatives on this site.
So if you are trying to duplicate Remington factory loads, use Red Dot for target loads and TightGroup for Nitros.
Remington,like all ammo producers MAY buy partially completed gunpowder, then add ingredients, which they consider secret, to increase or decrease powder burning functions. So, even though a powder from an STS shell MAY look like green dot or red dot, without the colored dots, no way to tell if it EXACTLY same as STS powder. They do this so you will buy their product over another.
For example, Pepsi vs Coca Cola!
Keep smokin' 'em!
The factory will buy powder by the truck load or train car load, then use thier LABRATORY to get a working load that meets thier specs.
SO what they get powder wise may be close a canister grade that we can buy, but rarely probably never will it match a canister grade!
As I have understood all my life........
A powder company rarely(NEVER)makes a batch of powder that meets a canister grade.
What they do is blend several to many Batch's together until they have a powder that meets the the very strict specifics for the canister, so whehter you loaded a certain powder last week or twenty years ago, or every week for the last forty years, the same wieght of powder will give you the same results.
TO go on with Shooting Coaches comment about changing the bushing's, the only spec that allows a variance is the powder density, so the bushing that threw 20 grains of __________(every and any canister powder) this time you bought powder may throw 19 or 18 grains or 21 or 22 grains the next time you buy powder.
Big Az Al is not completely correct. A batch or blend of powder is considered "canister" grade (salable to consumers for reloading) if the results from a given weight of charge fall within a particular 25fps velocity range AND a 2500psi range. There are standards for density, but they are loose.
So the notion that "canister" grade Red Dot is so consistent that every batch produces the same velocity with the same components and weights is pure hooey. Anyone with a good scale and a chronograph can put the lie to that.
For example: the last lot of Red Dot I bought required two Hornady/RCBS bushing sizes higher to throw the correct charge weight AND I got 20fps average less than what I have come to expect from that load over the years. The same is true of all powders. Usually, they are more consistent than the example I gave, but sometimes they are worse.
I believe that an Alliant rep posted at shotgunworld.com that the 2 3/4 dram and 3 dram Remington STSs are loaded with a canister powder that's in between e3 and Red Dot in burn speed. So, to replicate the factory load, load all Remington components with the proper amount of e3 or Red Dot.