Wheelgun Wednesday: M.R. New System Arms Cucciolo – The World's Largest Revolver

Giorgio O
by Giorgio O

Welcome back to Wheelgun Wednesday, our weekly article series where we cover everything related to revolvers. Today’s topic is a look at one of the candidates for the title of “World’s Largest Revolver”: the M.R. New System Arms Cucciolo.

Wheelgun Wednesday @ TFB:

M.R. New System Arms Cucciolo – The World’s Largest Revolver – Cucciolo with a J frame revolver for scale. (Credit: Marco Rigido)

The Cucciolo – the world’s largest revolver?

Superlatives such as biggest, largest, and most powerful are attributed very loosely to firearms, and there’s always someone ready to challenge the claim after drawing out their well-honed “ackchyually…”. We acknowledge the fact that there have been revolver cannons or more common and practical revolving grenade launchers, so we hope the readers will forgive us if we use the manufacturer’s definition of “World’s Largest Revolver” and we don’t look for the category where it actually holds true.

The Italian name of this wheelgun is a tongue-in-cheek one, as it can be translated into “puppy” or “cub” (it reads as koocholoh). Definitely, the exact opposite image comes to mind when lifting this gargantuan beast of a firearm.

M.R. New System Arms Cucciolo – The World’s Largest Revolver – Cucciolo from the loading gate: note the thick chamber walls. (Credit: Marco Rigido)

Cucciolo is a 5-shot, single-action, 12 gauge revolver. Unlike slightly more famous revolving shotguns, this model is designed to fire slugs out of hot-rodded, 3.5″ brass cases. With the goal of handling substantially higher pressures than conventional 12 gauge loads, the cylinder, frame, and rifled barrel are overbuilt, leading to an overall weight of about 22 kg (48.5 lbs).

M.R. New System Arms Cucciolo – The World’s Largest Revolver – Loading. (Credit: Marco Rigido)

While the form factor is that of a pistol, with no stock, Cucciolo is meant to be shot like a rifle, and this is accomplished with a sturdy steel structure acting as a bipod. Even though definitely heavy and unlikely to jump upon recoil, the gun is equipped with an artillery-like muzzle brake, surely capable of taming the kick… and making the shooter the most beloved person on the range.

Here below, in a dated video, we can see the only public footage of this revolver being shot. We can notice that the roaring beast is indeed gentle on the shooter.

Face to face with the puppy

Playing with the Cucciolo is quite an experience and probably a good workout. The revolver alternates accurate execution with very utilitarian details, such as the welded, reinforced, frame that more than a bipod recalls the central stand of a large motorcycle. Overall it gives the feel of a highly coveted weapon in a post-apocalyptic video game, one that you can handle only after achieving a certain level of experience.

M.R. New System Arms Cucciolo - The World's Largest Revolver - Balancing Cucciolo. (Credit: Giorgio O.)

Cucciolo has an 8-pound fixed cylinder, loaded and unloaded from a gate on the left side of the recoil shield. The gate swings backward, unlike more traditional designs where it opens outward. As is typical of high-powered custom big-bore revolvers, the timing notches on the 5-shot cylinder do not weaken the chamber walls, guaranteeing uniform strength.

M.R. New System Arms Cucciolo - The World's Largest Revolver - Loading the long shell. (Credit: Giorgio O.)

The controls are very stiff and trying to arm the hammer without having the firearm on a bench is quite a chore, both for the power of the spring and the cumbersome handling caused by the frame size. Fanning from the hip is unlikely to be an option.

M.R. New System Arms Cucciolo - The World's Largest Revolver - Attempting to arm the hammer. (Credit: Giorgio O.)

The .728 MR

Cucciolo’s actual caliber is .728 MR, a higher pressure version of a 3.5″ full brass shotgun shell, topped with a slug. The cartridge name is used by Mr. Rigido to identify his high-pressure loads, but for the authorities, this is still a 12-gauge, an approach that greatly simplifies the bureaucracy behind this development.

As with any 12-gauge, the .728 MR is highly versatile and it can be loaded with a wide range of slugs, both dedicated or designed for traditional shells. Loaded to about 26,000 psi, with the right slug weight (up to 925 grains or 2.1 ounces), the round can develop muzzle energies competing with the most powerful Express rifles. As a reference, the maximum pressure that SAAMI allows for 3.5″ 12 gauge loads is 14,000 psi.

Over the years, Marco Rigido has tested a variety of loads, both in the Cucciolo (definitely the best platform for the most powerful loads) or in custom O/U shotguns. What we can see here is only part of the collection of tested slugs, and the only fault that we can find him is not having an active YouTube channel showing how these perform in various targets.

M.R. New System Arms Cucciolo - The World's Largest Revolver - A .728 MR mock-up round with a selection of suitable slugs, from conventional to experimental. (Credit: Giorgio O.)


What do you, TFB readers, think of the Cucciolo? Do you agree with considering it the “World’s Largest Revolver”? Or do you know other competitors to this title? As usual, let us know in the comments section.

Giorgio O
Giorgio O

Italian firearm enthusiast, Giorgio has a passion for innovative or plainly unusual mechanical solutions. He's also interested in manufacturing technologies with a recent focus on additive manufacturing.You can contact him at giorgio_o at zoho dot com and you'll find him in the comments section as Giolli Joker.

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