I use Gordons reloading tool to see how my recipes are affected by all sorts of changes like seating depth or brass case volume.
According to GRT, small seating depth changes do affect pressure and thus velocity. Well duh but by how much?
If you are comparing recipes, The spec that matters would be case volume once bullet is seated.
I want to change my projectile type on one of my recipes. Same weight.
I am going from a JHP to a round nose bullet.
I opened my recipe in GRT, changed the bullet setting and set the effective seating depth to the same as my JHP recipe.
The seating depth measurement changed from 1.10 to 1.15".
And the pressure and velocity are more or less the same.
So according to GRT, I can use the same charge with the new bullet if seating to 1.15".
I will build a ladder anyway. But the data is useful to me.
Point is, the case volume and effective seating depth of the recipe are important to the result.
As well as barrel length.
eta.
I do not rely on GRT for safe loadings. I use GRT for relational information.
When creating a new load, I utilize multiple sources of load data to determine a range and then load a ladder.
I run a Combat armory 8" barrel and a YHM BCG.