Have never seen an M25, may have read a review but not sure. If 223 and 204 are factory chamberings then rebarreling or boring to a larger caliber based on those cases should not be a problem as long as you do not try pushing the limits. If you want to run them at max pressure continously then pick a known strong action to maximize safety.
If you want to use the M25 because of it's size then just be reasonable with your loads and enjoy.
2120-September 1, 1945
To: D A MacArthur /C H Nimitz
From: H S Truman
Political Correctness is a doctrine, recently fostered by a delusional , illogical minority and promoted by a sick mainstream media, which holds forth the proposition that it is entirely possible to pick up a piece of cr*p by the clean end!
Now, with special thanks to the Truman Museum and Harry himself, you and I finally have a full understanding of what "POLITICAL CORRECTNESS" really means.....