You would do yourself well to pay close attention to any powder changes, even within the same lot #!
And this goes especially for any of the Reloader and Accurate Powders. No two kegs are created equal, even within the same lot#. Years ago I started blending most of the powders I use. I am fortunate, I actually run pressure equipment here and able to get pressure data. Like most of us, I have been lazy at times, and just used the same load I had previously done pressure work on, when getting a new batch of powder, this caused an issue and an increase of 10000 PSI as well. And when you are working at 45000 PSI, an increase of 10000 PSI is subtantial and could lead to problems. On this particular load which was 42 grs of this powder, I had to back down to 39 gr to equal the previous 42 gr load. On another occasion in a larger caliber I had worked up loads that were perfectly safe at 62000 PSI with a 115 gr of this powder, from One, 5 lb keg. I eventually used that 5# Keg, and started with another one, but fortunately I did drop the charge. Had I used the 115 gr load with the new 5# Keg, it would have blown the rifle. I had to drop to 95 gr of the same powder, new keg, to equal the same velocity and pressures! On the next 5# keg of the same powder, it had to be lowered to 85 gr to equal.............. This could have led to a dangerous failure. I had to start load data on this cartridge over, and had to discontinue use of that powder completely. I still look for that very first Magic 5# keg, even blending different powders together, but I have yet to be successful in finding that magic 5# Keg that I started with.
I have not seen extreme changes in the IMR, Hodgdon, Winchester, or Ramshot powders. Minor differences yes, but nothing that would cause extreme concerns.
Regardless however, I blend all Reloader and Accurate powders. I blend IMR, Hodgdon, Winchester and Ramshot powders that I tend to use a lot of. Those that I do not use a lot of, I watch and test carefully when changing from Keg to Keg. I don't even pay attention to Lot#s anymore, I have seen major differences within the same lot#. We must keep in mind, before we receive a given powder, we do not know how it has been kept and the environment it has been kept in previously.
I have a clean uncontaminated 5 gallon bucket I use to mix and blend in. RL 7 is a powder I use a lot of, so I normally purchase 15+ lbs, pour it all in the bucket, mix it up thoroughly, and repackage it, and label it the day or month blended. Then it is off to the range and using the pressure equipment test the loads for the New Batch. Data kept from then on in that cartridge, references the Batch Date in each entry.
Accurate 2230 is not a powder I use much of. It is or has been decent in 458 Winchester, and that is all I have ever used or tested it in. In 2013 I did a lot of data work with 458 Winchester and used some 2013 Vintage AA 2230 in some of that work. I had previously found some serious differences from 2011 Vintage AA 2230 to 2013 Vintage, by 3-5 gr of powder and 5000-7000 PSI. In 2022 I wanted to do some new 458 Winchester pressure data and elected to purchase some new AA 2230 for that. I did a comparison between 2013 Vintage and 2022 Vintage, and found the 2022 Vintage gave 5000 PSI less pressure than the 2013 Vintage, with only 30-40 fps less velocity with the same bullet. This was a plus I suppose. But, it shows you cannot just change powders without checking it and using safe practices.
And below, you can easily see a vast difference in the two Vintages of 2230.
Yes, making a powder change, I would pay very close attention, not just Lot# to Lot#, but from one can of powder to the next. I strongly recommend using larger 5# + kegs instead of 1# cans. Yes, you should drop by 10% to test. At minimum. If below where you were, work your way back to the velocity you were getting.
Primers within the same make and #, has never shown to be an issue. For instance, I have never seen a major difference in Federal 215s from one to another. Primers can be an issue if you were going from Federal to say Wincheser or CCI, or reverse.
Brass can be a big issue too, I think I have seen more of a difference in changing from one manufacturer of brass to another than primers. All brass is not created equal.
