Gentlemen:
My sincere apologies for misuse of the term "MonoBlock"; my background is not that of a gunsmith, but rather that of a very interested shotgunner with a rabid case of the "double gun disease" and no talent for fine gunsmithing skills. All I can attest to is that the ribs and hanger lug were removed from the original Lefever Damascus barrels, the Damascus tubes then amputated forward of the barrel flats, new steel tubes were then fitted to the "breech piece", the ribs and hanger lug soldered to the new steel tubes, and barrels then finished and slow rust blued. The gun looks and shoots fantastic; and if I had the skills to post pics here, I'd certainly share same.

2-Piper:
Buck may very well have also used a set of Smith barrels in his experiments, I honestly don't know; but when I visited his shop back in the early 90's he showed me his Lefever "test gun". He'd stripped all the furniture and parts off the gun save for those actually required to make the gun function/fire; and its barrel bores were indeed pathetic. Buck also showed me the old tire out back of his shop to which he secured the gun for testing purposes; as well as the cedar tree he used for cover when pulling the lanyard attached to the gun's triggers. We discussed his experiments at length; and one result of those discussions was that I became convinced that a sound set of Damascus barrels could safely absorb proof level loads, and therefore should certainly be safe for use with low pressure smokeless loads. And as FYI, all these discussions took place long before I had the opportunity to read of Sherman Bell's experimentation with Damascus barrels in the DGJ. Had I known, or had this information in the mid-80's I'd have never had those fine old G Grade Lefever barrels sleeved/"mono-blocked"; as they were virtually mint. It is said we "live and learn but that G Grade Lefever is a story in itself, as it represented my double gun "awakening" so to speak; as prior to meeting a Florida collector, Garfield Beckstead, at that 1984 Gainesville, GA gun show and seeing my first ever Optimus Grade, I was convinced that only Parker guns were worthy of my attention. That Optimus opened my eyes to the fact that other domestic makers could, and did make fine guns also; and it wasn't long thereafter that I became quite bored with Parker guns to the point that I no longer owned one. As I visited with Mr. Beckstead and learned a little about the wonderful world of Lefever guns, he produced my G Grade from beneath his table; an absolutely wonderful gun with gorgeous and unusual English walnut furniture, mint Damascus barrels, 80% original colors, perished Silver's pad, and no forend. When that visit ended Mr. Beckstead had my $400 (a lot of cash for such a gun 30 plus years ago) and I had that Lefever with not the slightest idea I would ever find a forend; but my quest to get that Lefever operational again eventually lead me to New Mexico collector Gene Sandlin, who introduced me to Buck Hamlin; and with whom I've maintained a friendship ever since. Perhaps the most rewarding aspect of double gun collecting is the wonderful, talented, and fascinating people I've met as a result of this hobby; people I'd never have had the opportunity to meet and fellowship with otherwise. Got so much to be thankful for!