Well, from what I can tell so far is that the spring resistance is not a problem with a larger and heavier rotating mass. It must be like a flywheel affect going on or something.
If you look at the more modern Gatlings, they go both ways. The minigun firing pins don't move much more than a 1/4 of an inch or so and are automatic with the rotating bolt head that locks. When the bolt head rotates to the locked position, the firing pins are cocked compressing the spring then released then reset while unlocking and extracting.
I plan to remake some larger diameter bolts and try a different type of firing pin instead of using the mold ejector pins that I am using now. Not sure what, but they will be heavier like a AR-15 type or similar.