Here's another video that covers much of the same -
youtube/watch=aT21NrYQ6hQ He goes on about how used the gun is, but really it looks to be in rather decent shape.
G. Scott Jamison wrote two books about them, I have the first from 1988 but not the later one.
Bullard-Arms-G-Scott-JamiesonBullard-FirearmsI've never owned one but have handles a number of them at Rock Island Auction. These are a very smooth action but they have a 90° lever travel and the lever has a pivot point at least an inch farther out than any other action, add an inch or so to the lever on other guns and I think it they would feel smoother. Most of these I've seen are in really nice condition and show little use, RIA had some that had seen some use and I found the actions on those would hang up just before closing and the block at the rear of the bolt had to be pushed forward to get them to close. The tolerance's required for these to work also meant that once the parts wore a little they might start to have issues. The video mentions how well everything fits and that parts from one gun will probably not fit another. It's a very elaborate action with a lot of parts to wear or break.
The lockup on these is basically an rolling block single shot action placed behind the breech bolt, a block 'rolls' up and then an arm pivots in under it's rear to lock it, the block is pulled up by some gear teeth on the end of the bolt and when these actions wear that block does not roll up far enough to allow the locking arm to swing under it. The bolt must go fully forward for the action to lock-up on it's own and wear on any of the several parts doing this in this very complicated action will cause issues. This feature is also why it was easy to also make a single shot, since the rear of the action was basically for a single shot already.
The rolling block type locking also makes me question the strength of these, it can't be any stronger than a rolling block action and the pins look smaller than used in most rolling blocks so it might be weaker. It's basically a Laidely type rolling block action which has the hammer pivoting independent of the locking based on the Laidely & Emery patent from May 15, 1866.
The action uses other features from older designs going back as far as the ring trigger Jennings patented Dec 25, 1849,
US0006973, - it used double racks with a common pinon but the pinion was fixed and the rakes moved with the lower rack going forward to move the breech block rearward. Another is for breech loading percussion rifles patented by T. Bailey on June14 1859,
US0024437 - it covers 3 different uses of two racks with a movable pinion, one moves the barrel forward for loading. The lifter design goes back to the Smith & Wesson lever action pistol patented in Feb 14, 1854 and the Henry and early Winchesters.