Well, I remove and examined the magazine and follower. The follower appears very generic and I see no reason why it would need to be changed.
The only thing that seemed wrong was the feed lips.
Being that the magazine is basically worthless as-is anyway, I decided to see if I could just make it work.
I used some 243 cases and slowly bent the feed lips until they appeared to fit the 243 case the same as they had fit the 270WSM case.
The magazine now works fine with the 243 cases. I probably won't know for sure until I get the proper bolt head installed but I don't see any reason why it shouldn't work.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.