Everything about this makes me cringe. I have spent a lot of time loading for my 25-35 hollenbeck and less time with my 30-30 and 32-40. ALL SIGNS POINT TO DO NOT OVERLOAD. What I would have considered 70% loads in the 25-35
Caused case deformity, rough extraction, deformed rims, and damaged case necks. Also the chamber on that gun requires a very short OAL such that modern (1960s) factory loads will not close in the gun (117 gr bullets).
On the shotgun side I wouldn't put ANY heavy, magnum, or otherwise big load in it and I am referring to 2 3/4in 1 5/8 oz type loads. 3in is totally out of the question in any form.
I do not consider myself extreme or overly cautious. But I error to the side of caution