Let's see what we have learned here:
1. Now the moderator of this forum, Jack Roberts, says: "...pay more attention to those who have done it repeatedly with at least a few AI chambers"
Guess what?, I HAVE worked with AI chambers, so its interesting that one presumes I haven't done so despite my previous posts that never indicated I was inexperienced or experienced with AI chambers....
Can you observe how mislearning happens i.e. folks just presume without any facts?
2. I have been reloading since 1983 and reading literature on it since then; when did the moderator and posters start to reload? See, I am now asking for facts as to the degree of their experience...I am presuming nothing.
3. The central theme of reloading is safety first, and within that, start at a known safe level [establised in load manuals by ballisticians/engineers smarter than me and you and with access to labs and test equipment] and work your way up while monitoring for known pressure signs.
4. Poster Hunt accurately notes there is "no pressure data..." in his manuals for the 223 AI caliber [SAMMI pressure data for the standard .223Remington applies to any .223AI action so use that as the baseline, generally true for any AI caliber ]. Thus, shooter observance of any and all pressure signs per the incremental load workup methos is all the more important. You have few, if any, labs testing with AI cartridges (22/250AI an exception per the Nosler #4 manual...). Remember, though, ALL GUNS ARE DIFFERENT.
5. Poster Brdeano and others note that the "pressure " was too much in their 223AI barreled action with .223 R cases that were loaded to the 223AI level i.e. beyond-maximum fireform loads...in fact, it is likely no more "pressure" than a standard .223R cartridge BUT now an uncontrolled spike in pressure exceeding the chamber design.
Such an effort is using the .223R case with almost no shoulder support[barely] in an AI chamber...all the support is nearly absent until fireformed. Thus, support is at the lands and the bolt face, case base only when fireformed, and a .223 AI level load is sure to exceed headspace safety as the shoulder support is [almost] non-existant. Thus, what appears as "pressure" is really human error exceeding the safety of the safe fireform method.
The longer throat of the AI chamber noteed by poster hunt is not enough to overcome this error and prevent a likely headspace issue and a ruptured case