Obviously not all set in stone, but me still being so new I enjoy plugging in all sorts of information and seeing how it changes things. I have some Speer nickel 223 cases I'm loading up with some 75 grain Midsouth black tips and playing with powders and various things because there's no direct published data. Anyhow, all this Speer brass was from factory Gold Dot 55gr ammo I've shot once but it measures 1.74" cases and published case trim length is usually 1.75". I guess the nickel plating changes the case so that it didn't stretch when sizing it even with a small base sizing die. So I changed the case length in GRT from 1.75" to 1.74" and pressure went down by 531 PSI. Probably not enough to worry about with 23.6gr of W748 but it made me think of some threads here where people talk about not trimming their brass as long as it's in spec and I wonder what the real world effects are on larger cartridges with more powder capacity and figured I'd check here to see if anybody had some wisdom to spread with that. I'm sure it's due to less/more material gripping the projectile, which also makes me consider the fact that I'm planning to crimp these things as well and makes me think about case neck tension on my other loads.
edit: Also GRT defaults the case volume to something like 31gr H20 and I measured these cases and weighed them with water and came up with 29.6gr H20. When I changed that it added about 6800+ PSI to the data.
edit: Also GRT defaults the case volume to something like 31gr H20 and I measured these cases and weighed them with water and came up with 29.6gr H20. When I changed that it added about 6800+ PSI to the data.
