My .338 Thor

With the 338 Thor without the dies I'd do a false shoulder and then COW method. That gets you to where the hydraulic dies will get you. On a cartridge like the 338 Thor I'd opt for the hydraulic dies. In the old days when components were cheap and easy to get COW was more viable. Now I'd go with the dies. The only reason I went with jamming was I got my bullets for real cheap, less that 90 bucks for 500 shipped because they were damaged on arrival. I figured for steel and varmints out to 500 yards they'd be okay.
 
With the 338 Thor without the dies I'd do a false shoulder and then COW method. That gets you to where the hydraulic dies will get you. On a cartridge like the 338 Thor I'd opt for the hydraulic dies. In the old days when components were cheap and easy to get COW was more viable. Now I'd go with the dies. The only reason I went with jamming was I got my bullets for real cheap, less that 90 bucks for 500 shipped because they were damaged on arrival. I figured for steel and varmints out to 500 yards they'd be okay.
Yep, that is exactly what I did in #48.
 
OK. I'm just trying to understand how close the hydro forming get's you to the final improved case dimension. If I were to ever do another wildcat, it would be similar to this, but probably in a 30 cal.
That's why I provided pictures of the "actual" formed brass achieved after the hydraulic forming process (middle), next to a parent case, and after fire-formed off the chamber. My other hydraulic forming die is a .30 cal wildcat (.30 LARA) made by Whidden.

338-nm-vs-hydraulic-forming-die-vs-fireforming-jpg.448878
 
I see what buckbrush is saying; with the hydro form die you're not getting a fully formed case as far as your capacity numbers are concerned.

I did the same sort of project off a 338 Norma Mag but I didn't move the neck/shoulder junction forward and went 35*. To start I took 3 pieces of brass and created a false shoulder on the neck and fired them each 3 time's partially neck sizing in between. I sent that fired brass to Whidden to get hydraulic form and full length sizing dies made.

I haven't measured the capacity along the process like Feenix did but I like the hydro form process. You can blow out the shoulder and then size the case back to where you get a crush fit for your initial firing on the case. No messing around creating a false shoulder and all that. I have hydro formed all my brass and am in the process of firing those 100 pieces before I do any real load development. Essentially I'm hydro forming then fire forming before I consider the brass fully formed.

If I was COW forming I would do the COW load then a forming load with bullet jammed on all the brass before considering it fully formed and ready for load development. So with the hydro die I'm saving myself that 100 (or however many pieces of brass) shot with COW as an initial form.

I think I may reserve 25 or so cases that are only hydro formed to see how they compare to the fully formed cases after I have developed a load. In other words once I have done load development in my fully formed brass I'll load some hydro formed brass with the load I found and see how it compares between once fired (fully formed) and not fired just hydro formed brass.
 
If I had to guess capacity changes from just the pics, I would bet the virgin to hydro would be like +5 and the actual fire forming another +2-3
 
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