forming 7mm tcu?

[tree rat]

I do not have the barrel yet, but I have come across a bunch of .204 ruger brass (hornady) I know the shoulder is a little longer than .223 . My question is can I run .204 ruger into a 7 tcu full length die? I realize I will probably have to trim because there longer o.a.l. than .223

[Gavinator]

 Yes.
 As the case mouths are opened the case length will shorten.
 Better if these are once fired cases, as the extra diameter will help support the case as you move the shoulder back.
 Use "Imperial sizing die wax" to help keep from buckling cases.
 If cases buckle use a .223 die as an interim step.
 Before you set the shoulder back you should have the barrel there off the frame so you can make sure you're not setting it back too far.
 I don't think you'll be able to fully form the 40 degree shoulder, and the cases will shorten again when fireformed.