Mainly to help in deciding what powders I should be using and to help find good starting points when loading. I'll use 6mm-284 as an example. Hodgdon lists data for this round but it lists cartridge overall length as 2.750. My overall length with either 90 grain NBT or 100 grain Sierra soft points can run up to 3.030" (that's right at the lands). Some have said to use 240 Weatherby load data as a start point. Ok, well Nosler lists the 240 as holding 60 grains of water. My old W-W cases hold 64.3 grains and my Norma cases hold 66.2 grains. This has to account for something, and from my first crack at using Nosler's 240 data was underwhelming to say the least. Using their maximum load of RL19 (52.5 grains) netted me barely over 3100 fps. This somewhat illustrates my point, using the 240 data should've put me in the 3400 ballpark but when I mix in greater capacity and quite a bit more generous freebore I come up way short. I 've been having understandably better results with H4831, but I'd like to spend less powder (and barrel life) finding where the max is with my combinations.
Ok, maybe I just want something else to play with but hey it sounded like a good pitch.
Ok, maybe I just want something else to play with but hey it sounded like a good pitch.