Neck-up 300 RCM brass to 338 RCM?

[calinb]

I got a Ruger M77 Hawkeye in 300 RCM and a lifetime supply of brass and ammo (figuring that 300 RCM might become orphaned).  I like it so much that I'm thinking about getting a 338 RCM.  Might I be successful necking up my 300 RCM cases with annealing, full length sizing, trimming, and fire-forming all at my disposal? 


http://www.saami.org/PubResources/CC_Drawings/Rifle/300%20Ruger%20Compact%20Magnum.pdf


into


http://www.saami.org/PubResources/CC_Drawings/Rifle/338%20Ruger%20Compact%20Magnum.pdf


Of course, I'd need to be able to push the 300 RCM shoulder back before I could even chamber it in a 338 RCM.  Would this best be done in stages or just one big push of the press ram?


I've necked up 223 WSSM brass to 243 WSSM but this seems like it might be a bit more work, because the shoulder is somewhat deeper in the 300 chamber than the 338 chamber.  The angle is the same but, essentially, a 338 RCM case is a bit shorter than a 300 RCM case.


Thanks for advice from the many here more experienced than I.


-Cal

[calinb]

I decided to try to push a test case's shoulder back.  Not having a 338 RCM die yet, I removed the expander ball from my 300 RCM die and rested the case on a plate of metal on the press ram, to get more insertion of the case into the die.  Even after the annealing the case shoulder, I could not push back the shoulder substantially with maximum effort on my Lee turret press.  For kicks, I will try more force using my hydraulic press in the shop later today.  0.074" is what I need.  That's alot of shoulder movement!