I recommended braizing it together.
Braised a fitting onto my school made potato cannon, if it can launch a potato 150-200m, im sure it can take someones fingers bashing on it
Twas a suggestion, he wants a blade trigger, and hes going to have to make his own trigger fairly thick to avoid bending, so instead of sawing through maybe 1.5 or 2cm thick of metal, it could be an idea to make a template and split it into bits.