DeHaas spoke highly of the Hepburn actions and considered them as strong as other falling block actions. He didn't care for the firing pin design, but can't say as I agree since I've never had any issues with Hepburn firing pins. But then he was looking at how a Hepburn could be rebarreled for modern high pressure cartridges when he wrote about the firing pins.

Many moons ago, I had a friend who had a custom varmint rifle built on a Hepburn action.  This included bushing the breech block for a smaller diameter firing pin.

The caliber was .22-33/30 Ackley Improved.  I don't know what his load was, but I don't think he was bashful.

Strength was not a problem, but the upward angled firing pin had a tendency to hang up in the fired primer.

I would consider this to be a rather extreme example, but a data point nonetheless.

Curly