Bramble:
Well spoken post. This is stuff that needs saying.

The shottie action which started this post (CZ or Huglu) has a relatively long action-bar, side-clips and Greener cross-bolt, and has the correct number of triggers as standard. Maybe even ejectors if you want them. Looks good so far. However, is it 4140 or 4130 steel, or some other alloy? Sounds like you would need to know this. On the previous thread referenced above, Bonanza suggests "The CZ action is made from 4130 or 4140 heat treated chrome molybdenum alloy steel". Still looking good, then.

Remember too, the issue is not the proof-pressure of the donor shotgun's action/barrel-group, it is the proof pressure you will use to prove the newly-built DR. Determining whether the DR will survive proof is probably not possible before commencing the build, but Bramble has added a few more valuable pieces of data to help exclude unfavourable or potentially unsafe shotgun actions.

...and despite all this, like 400NE I am personally inclined to recommend restricting such conversions to N-for-B loads. In the larger calibres, they are still magnificent killers of game up to buffalo and brownies with the right bullets.