Re: load develooment with unfired brass???
In practical terms, I'd say you can; at least for the first round of ballpark/pressure testing, where we are looking for a coarse approximation before settling down to finding a more precise match to barrel harmonics. By that time, you should have enough fireformed cases to proceed to the more precision development stages.
When I do load development; I actually try to avoid highly complex, precise, and demanding handloading steps. I do this from a logical perspective. I figure that if a load requires such backflips to get it to work right, it's not the kind of robust and dependable load that I can depend on not going to go out of tune on me when small environmental condition changes occur.
When you get several decades down the handloading road, you begin to realize that you've made a bunch of ammo and it's all mostly gone the way of the dodo. Handloading can be an end in itself, or a means to an end. I prefer the latter, see the real end as the shooting, and try to keep the handloading as basic and simple as possible.
There's an accuracy sacrifice, of course there is. But what some folks tend to overlook is that said sacrifice doesn't actually need to be that much, and that the shooters who can tell the difference aren't exactly thick on the ground, either. Mother nature and human frailties will often combine to eradicate said difference more often than we like, or may be willing to anticipate.
So, in other words, I combine my fireforming with early-stage load development, and when I have the load, will incorporate new cases directly into production. You may or may not note differences at that point, but as long as you know and can recognize them, you can anticipate their effects. If fireforming production cases becomes a genuine necessity, this will become readily apparent soon enough.
Greg
