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What is the Difference Between Demi-bloc and Monoblock Barrels?
Exploring the barrel making process for double-barreled shotguns
The first time I heard the word demi-bloc, I was standing on the production floor of AYA shotguns in Spain shooting a film. I am admittedly something of an amateur when it comes to double guns.
“If it hits birds, that works for me,” is about as advanced as I knew growing up. Looking back, I had shot some guns with demi-bloc barrels. But past my initial curious, “Did this gun hit anything?” reaction, I never investigated. So, on this day I continued my deeper dive into understanding the technology of shotguns—barrels being unquestionably one of the more important parts!
At its basic core, “demi-bloc” refers to a method of barrel construction and is sometimes referred to as “chopper lump.” The more popular method is called “monoblock.” What is interesting here is the etymology of the word. “Demi” means “two” (half) and “mono” means “one.” That would instantly lead one to believe (at least me) that one sounds better than two. And that is not necessarily the case, nor (as it turns out) even an accurate mental picture.
In the case of a demi-bloc barrel, it’s formed from two solid pieces of steel joined together to create a double-barrel shotgun. The continuous metal grain that occurs along the whole length of the barrel produces a stronger final product. The process of joining the two barrels is very much the handiwork of highly-skilled craftsmen. On the floors of AYA, the barrels were joined with silver (although I did expect to see them melting the equivalent of my grandmother’s silverware down somewhere, it was actually long pieces of silver wire).
If you look closely enough on a side-by-side shotgun, you can see a very thin line (up and down) between the barrels at the breach when opened. This is where the barrels were joined. Monoblock, which is the common way to make over and under shotguns, can be a little easier to detect. A single piece of steel is used to create the monoblock, essentially from the base of the chamber to the end of a shotshell. The barrel tubes are then joined into that single piece which creates a visible joint (sometimes hidden with engraving) on the outside of the barrel. Back to the deception of etymology, the demi-bloc is in fact two pieces for the whole barrel process, whereas the monoblock is three. Go figure. However, monoblock allows for the use of two different types of steel while the demi-bloc is restricted to one.
Demi-bloc has its biggest advantage in strength. The “bite” of the shotgun joins both halves of the barrels to give added support when a cartridge ignites. Add in the continuous metal grain and, by definition, it becomes a superior product.
Now, all this makes demi-bloc seem like the coolest kid in school, and maybe back in the day, that was more accurate. The reality is that between the quality of steel and the computer-automated precision of monoblock construction, the level of tolerances that can be perfected on a monoblock is truly a modern marvel. Still, the idea of the hand-constructed craftsmanship of a demi-bloc barrel has a certain level of nostalgia while still being mechanically sound.
This whole process can also apply to over-and-under shotguns by simply turning everything on its side. That, however, can call into question the significance of the strength of demi-bloc construction. The bite no longer holds both barrels, the top barrel being reliant on the braze between the barrels.
Some gunmakers, like the Italian shotgun company RFM, offer shotguns with choices in both monoblock and demi-bloc.
At the end of the day, it’s the 21st century. There can certainly be personal preferences from demi-bloc to monoblock, but to a guy like myself, it’s tough to feel a real difference when shooting. In the end, the combination of both brand and quality can turn out a really good shotgun using either method.
A.J. DeRosa founded Project Upland in 2014 as an excuse to go hunting more often (and it worked). A New England native, he grew up hunting and has spent over 30 years in pursuit of big and small game species across three continents. He started collecting guns on his 18th birthday and eventually found his passion for side-by-side shotguns, inspiring him to travel the world to meet the people and places from which they come. Looking to turn his passion into inspiration for others, AJ was first published in 2004 and went on to write his first book The Urban Deer Complex in 2014. He soon discovered a love for filmmaking, particularly the challenge of capturing ruffed grouse with a camera, which led to the award-winning Project Upland film series. AJ's love for all things wild has caused him to advocate on the federal and state levels to promote and expand conservation policy, habitat funding, and upland game bird awareness. He currently serves as the Strafford County New Hampshire Fish & Game Commissioner in order to give back to his community and to further the mission of the agency. When those hunting excuses are in play, you can find him wandering behind his Wirehaired Pointing Griffon in the mountains of New England and anywhere else the birds take them.
Nice article explaining the difference between demi-bloc and mono-bloc construction.
A list of makers of each type would have also been very informative.