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2-piper...thats a good question...I don't understand either..I base my idea of demi-block on the Sauer and Pieper patents and those unappealing robust shotguns where Manufrance plugged 16ga tubes into a 12ga block...Have you seen those clunkers? If I bought a gun as chopper lump and a demi-block arrived, I would send it back...My first responce to reading that was...it's an error in translation and I know better...but how can I second guess FN...How can a demi-block also be chopper lump? what would be the point of splitting the block...I say we get a good look at sxsman's FN...look at the lumps to see if they are split, and look at the tubes 3 inches from the breach, to see if, in fact, it's a demi-block...send me a blank email with the subject as FN and I will send you those pages from the catalog...then we'll scrutinize his FN...hows that sound?

Demi-bloc Barrels - (called Chopper-lump barrels in British) - A method of joining the two separate tubes of a set of barrels where the right-hand half of the pair of lumps under the barrels are forged integrally with the right barrel and the left-hand half of the pair of lumps under the barrels are forged integrally with the left barrel. Chopper-lump barrels can be recognized by the fine joint-line running longitudinally down the center of each lump. This method of jointing barrels is the best because: 1. It is the strongest in relation to its weight, and 2. Because it allows the two barrels to be mounted closest to each other at the breech end, reducing problems regulating the points of aim of the two separate barrels.

http://www.hallowellco.com/abbrevia.htm#DA

To go along with what Randall said here are a couple of pictures that show what is meant by "chopper lump".

Robert,
My FN boxlock does not have the chopper lump barrels, Lumps not split.
How do I recognize a demi-bloc barrel?
Pete

The 1909-1915 [approx.] catalogs of Stevens , with their 365, 375, and 385 models show illustrations of what they considered demi-bloc. I am 3000 miles away from my catalogs, so can't show you.

OK.2-piper..now I understand...demi just means half...in either direction...Demi-block can be either...Either the block halved with the tubes or the lumps halved with the barrels. Both qualify as demi-block....but chopper lump means specifically one design of demi-block, and that is each halve of the lumps are machined or forged integrel with each barrel...

Robert; I think you have it there. Also unfortunately all makers do not always follow the same terminology & meanings change over time. A very good example of this is "Double Action Revolver". "Originally this meant a revolver which could be fired by either of two action types ie by either hand cocking or firing by a long trigger pull. What today is referred to as "Double Action Only" was then a single action, as it had only one mode of firing ie by a long trigger pull.
Chopperlump was I think primarily a British term, they were I think the only people to call an axe a chopper.

This is for all you guys who followed this thread any came away with nothing to bolster your files on FN SxS's

sxsman1...Here is FN's patented chopper lump system. The system shown in this patent is not obvious in the catalog drawing...it's an axial double dovetail system, with what looks like a curved drive wedge ...(I didn't understand 'til I got the two halves of the drawing together)...

Note the telltale 'joint line' or seam is still clearly visible in the finished product.