The revolver world's best-kept practical secret is the convertible: a revolver shipped with two cylinders — or one cleverly-chambered one — that runs entirely different cartridges from the same frame. Rimfire convertibles pair .22 LR with .22 WMR; the modern centerfire version adds the more interesting trick of running 9mm through a .38/.357 revolver. Here's how the breed works, and who genuinely benefits.
How one gun runs two cartridges
A revolver's barrel only cares about bullet diameter; it's the cylinder that must match a cartridge's case dimensions and headspacing. Convertibles exploit that split. Ship a second cylinder machined for a different cartridge of compatible bullet diameter, and swapping the cylinder — seconds on most designs — re-chambers the entire gun. The rimfire pairing works because .22 LR and .22 WMR share bullet-bore compatibility while being chamber-incompatible (the safety issue our rimfire magnum guide details, which convertibles solve properly). The centerfire pairing works because 9mm and .38/.357 bullets are near-identical in diameter — close enough that one barrel serves both honestly.
The 9mm cylinder: why bother?
Because 9mm is the cheapest, most available centerfire pistol cartridge on earth, and .38 Special isn't. A 9mm-capable revolver plugs a wheelgun straight into the ammo ecosystem every semi-auto shooter already stocks — shared ammo with your carry pistol, bulk-market pricing for revolver practice, and one more gun that runs on the calibers your safe already buys deep. For households running both platforms, that logistics argument is the entire pitch, and it's a good one.
The catch is mechanical and worth understanding: 9mm is a rimless cartridge, and revolvers extract by the rim. The standard solution is moon clips — thin spring-steel stars that hold a full cylinder's worth of 9mm by the extractor grooves, giving the ejector something to push against. Moon clips carry a bonus and a bill. The bonus: a loaded clip is effectively the fastest revolver reload there is, dropping all chambers in one motion like a speedloader that stays with the cartridges. The bill: clips are consumable-adjacent — bend one in a range bag and it ties up the gun until swapped — and loading and unloading clips is its own small chore that dedicated tools make painless. Some convertible designs headspace 9mm to fire without clips, extracting manually instead; fine for range loafing, but the clip is the system working as intended.
The breed in the flesh
Charter Arms builds the idea in compact working form: the Charter convertible five-shot runs .38 Special and .357 Magnum through one cylinder and adds 9mm capability in the same package — a carry-size frame that eats three of the most common handgun cartridges in America. The value proposition is the same one our working-revolver reviews keep landing on: maximum practical capability per dollar, refinement rationed accordingly, and the expectation that you'll prove your specific loads in your specific gun before trusting any of them. With convertibles that proving matters double — each cartridge gets its own function and point-of-impact test, because the fixed sights split the difference between loads that fly differently.
Honest limits
- Point of impact wanders across cartridges. One set of fixed sights, two or three different loads — expect each to print its own spot, and know each spot cold.
- The swap is a bench task, not a battlefield one. Convertibles are about owning flexibility, not switching mid-string. Configure the gun for the mission before leaving the house.
- Clip discipline is real. Straight, protected, and pre-loaded clips or the 9mm advantage evaporates at the range. A dedicated pouch — same logic as our speedloader carriage advice — keeps the system honest.
- Feed each chamber its own ammo. The convertible removes the temptation to improvise. Stock both sides properly: the .38/.357 board for the revolver cartridges, your existing 9mm supply for the clips.
Bottom line
Convertibles are the revolver world's Swiss Army answer: one frame, multiple ammunition ecosystems, real logistics savings for multi-platform households, and — in the 9mm case — the fastest reload wheelguns offer, courtesy of the humble moon clip. They ask a little discipline in return: per-cartridge testing, clip care, and the understanding that flexibility is configured at the bench. For the shooter whose safe already speaks two ammo languages, the convertible is the interpreter.
Frequently asked questions
How can a revolver shoot 9mm?
9mm and .38/.357 bullets are nearly identical in diameter, so one barrel serves both. The gun needs a cylinder chambered for 9mm, and because 9mm is rimless, moon clips — thin steel stars holding the rounds by their extractor grooves — give the ejector something to push against.
Are moon clips faster than speedloaders?
Generally yes — a loaded moon clip drops every round in one motion and stays with the cases through extraction, making it the fastest reload in revolver shooting. The trade is care: bent clips cause problems, so they need protected carriage and occasional replacement.
Do convertible revolvers shoot both cartridges to the same point of aim?
Rarely exactly — different cartridges at different velocities print differently through one set of fixed sights. Test each cartridge you'll use, record where it prints, and prioritize the sight regulation for the load with the serious job.