I don't do it unless they have the same lot number, which sometimes mine do because I usually buy in bulk.I'm newish to reloading and was wondering if you can mix the last of a bottle with a new bottle of same powder.any words of wisdom would be greatly appreciated.
A very important point, this case capacity thing, especially with the different brands of .45-70.Along the same lines as switching powder lots with no regard, is the switching of brass with the same amount of concern - about zero - and this can also get you in deep do do.
Yes, I know that for the most part we all get away with it and have no visible negative results. However ------------
Some years back - 25 +/- - I was developing loads for a son's 30/06. We had about an hours drive to the range so wanted to make the trip worth the cost and effort.
Ran out of the Remington brass which was being used, so for the last two groups in the test series I went to the brass bucket for the needed brass.
I took care to sort the brass, same brand, same style head stamp, then trimmed to proper, "trim too length", and went ahead and finished the loading process.
Rather then using the 5 or so needed "odd" cases in just one of those last two groups, I seem to recall used 2 in the next to the last group and 3 in the final group.
The results make the point here. In the next to last test group, the "odd" brass opened the groups with maybe - ?? - some hint of pressure increase, while in the final group those "odd" cases gave excessive and very high pressures. So high in fact that one piece came out with a primer which looked like it had been riveted in place and that case stretched - in just one firing - to beyond the, "needs to be trimmed" length as well as throwing those shots waaaay out of the group.
I have never had this experience since and never before, but the point is it can happen and could really wreck your day or a fine rifle.
Today, with digital scales, we could weigh "odd" brass and likely avoid the potential problem by weeding out heavy/thick brass. How many of you weigh your brass? I'd guess few to none.
A better way is to keep you brass segregated by brand, lot number and times fired, at least for your typical center fire and high pressure rifle cartridges.
So, as I said earlier I have seen what I'd consider to be fairly large velocity changes with a change from one lot of powder to another, and have seen greatly excessive pressures caused by brass of an different manufacturing lot number, so it really does come back to being safe and no matter what or how we deal with the lot to lot differences in components, being aware that there is a proper and safe way and the way that most of us use and almost always get away with.
Be thankful that quality control is as good as it is, but don't bet you life on it.
Crusty Deary Ol'Coot
With .45-70 and my .223 brass I weigh the brass so it is .1 grain plus or minus. Winchester brass is so hit and miss I refuse to buy it. Remington varies enough that I often get 51-55 shells in a bag that is supposed to have 50. Hornaday match brass so far every case has weighed the exact same but when marked 50 casings i seem to get 48 to a box. Every loaded .223 round I use weighs the exact same to the box I make and put it into. The .45-70 I sue pyrodex and measure by volume and still check every loaded round. Handgun brass has never been consistent enough to try for me. Just my .02A very important point, this case capacity thing, especially with the different brands of .45-70.
I weigh cases on a digital scale, but not for a weight of the case, but rather tare the case off and weigh how much water the case holds.
I do this with at least 10 cases in a lot, get an average, and do peek at standard deviation to see how uniform that lot of cases is.