Changing powder lots within a powder

I've been stuffing powder in cases since the 70's. I used to run through a lot of rounds shooting pistol Silhouettes, never noticed anything I recall from from one lot to another, but it's been quite a few years back.

Same with my hunting rounds. Maybe if I was shooting bench rest I might be able to notice. I've loaded from 223 to 416 Rigby and in between.

Temperature, now that's a different story. Some hard lessons can be learned shooting top of the chart in August under that hot metal roof at American shooting in Houston Texas. What you can get a way with bear hunting in Alaska may not work in South Texas.
That's why I try to work up my max loads in July and August. When fired in cooler temps loads are pretty much all ways milder, so no suprizes.
 
X2! Mixing same powder in this manner has always kept my loads consistent since they were now "same lot". I also label with the date I mixed them and the lot numbers that were mixed. Just anal I guess to include lot numbers.
Good idea with the lots numbers you can check for a recall.
 
I've always had plenty of powder of the same batch on hand but with the way things are now, that can be difficult. Do you find when switching batches, of the same powder, that you can simply adjust your powder weight to the velocity you were getting before and your groups remain about the same or do you need to do a whole new load work up with eahc new batch change? What is your process for this? Thanks
I got lucky and scored on eight 1lb containers of h4350. I loaded up 20 rounds with it and zeroed in my scope. Sat down to load some more and saw that the next container was a different lot number, out of my 8 I had 4 different lot numbers. So I mixed them all together in an 8lb container and now I have a "custom" lot number that is absolutely all the same. I poured it all back into the original eight 1lb containers and labeled each accordingly. Like when I did it, crossed out the lot numbers on the container and wrote in the lot #'s that I had combined. The next 20 rounds I fired with the mixed powder grouped the same but with a slightly different POI. A little scope tweek and voila.
 
I don't generally don't get 1lbs powder containers, sometime you can't get around it. I have read here several time of mixing the same type of powder together. Can see where that wouldn't work.
 
I don't generally don't get 1lbs powder containers, sometime you can't get around it. I have read here several time of mixing the same type of powder together. Can see where that wouldn't work.
I thought I was getting an 8lb keg, but when the order arrived it was 8 individual containers, so I made the best of it.
 
Old lot vs new lot, by volume.

IMR 4198 ( 18.5 gr vs 19.6 gr.) and Alliant 2400 (13.0 vs 13.6).

There will be a difference in weight, old lot being lighter. Why? My guess is some of the solvents evaporate in the older powders. Or outgassing??

old post warning. Nov. 2021.
 
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