I had one about 25yrs ago, maybe more. A project gun that I never got to finish up. Sold off to another person with more time on their hands!
Opening the action with the lever moved the bbl set slightly foreward and then allowed them to drop down.
The breech face was made with round flanges for both chambers that the bbls set back into. That was the necessity for the bbl to push forward slightly before being able to drop down.
On closing the breech, you brought the bbls back up like any SxS. Then closing the lever pulled the bbl set backwards that small distance once again and the bbls engaged those protruding flanges in each of the chambers. I assume that was the 'Lock-Fast' idea.
Mine had an extra set of bbls that seemed to be an aftermarket make,,not quite right, but close and still 'in the white' .
The orig set if I am recalling the correct gun from those yrs ago had a name w/ Detroit, MI address on the top rib. I had never found any info connected to the name at the time.
I have seen the LockFast system used on a couple of the SxS handguns made in gauge bore sizes (Howdah Pistols?) Those back-up handguns for when hunting big kittys.
