09-29-2021, 11:19 PM
Charts are not really much good for anything IMO than somewhat relatives among the various powders. And I have not heard of single base burning "slower than the chart"... however, I have seen MV differences, thus burning difference of some kind, from equal loads of same powder but 2 different lots. Ex, for 123 sst and 1 lot of AR comp, 28.2 will give me 2510 fps. A separate lot of AR comp will give me 27.4 and 2520 fps - in that lot a 28.2 gave me 2580 and flattened primers. 0.8 grain delta means ~2-2.5% burning difference. Other powders, with 2 lots, might be much the same (I have a couple of H4831sc's like that). I don't know a rhyme or reason, you just have to do the chrony's yourself and see what they do in your rifle.