Imagine a scenario where you are low on ammunition. You used the last of your supply some time ago and despite your searching high and low for more, you have come up with nada. A gun without ammo is little better than a clumsy club, or an intimidation tool at best. You know you won’t be able to do what you need to do without ammo. Things are looking bleak.
Or they would be, if your gun was not multi-caliber capable. Since it is, you found another cartridge that your gun will take with little or no modification, so with a quick reload and maybe an adjustment or two you are back in business.
An adaptable gun in turn makes you more adaptable to your circumstances, allowing you to make better use of sometimes scare supplies of ammo or simply tailor your ballistic solution to the problem at hand.
In this article, we’ll be looking at the unique advantages provided to preppers by multi-caliber firearms, as well as considerations for selecting and employing them.
A multi-caliber gun is simply one that is able to accept a variety of cartridges with little or nothing in the way of modification, or if it is one that requires substantial parts swaps at least makes the process easy and quick at the user level.
Multi-caliber guns can run the gamut from handguns all the way up to rifles and even a few shotguns. Some guns are inherently able by design to chamber multiple distinct calibers, one common and certainly well known example being your run of the mill .357 Magnum revolver in whatever model it is encountered, all of them by nature being able to chamber the shorter, weaker .38 Special.
Some guns can accommodate a second or even third cartridge by simply changing a few parts, like the barrel and magazine, or in the case of revolvers the barrel and cylinder.
Magnum Research’s enormous Desert Eagle magnum autoloaders are one infamous example, with the frames and slides of those hefty guns able to accept multiple calibers with nothing more than rapid barrel and magazine switch.
Dan Wesson revolvers famously had easy to change barrel assemblies that facilitated caliber switches in certain models.
Break-action shotguns of certain make, like Browning’s Lightning over-unders were often sold as a set with multiple chamberings and barrel lengths. Today one of the most famous multi-caliber firearms is the ubiquitous AR-15 platform, which can chamber such a wide assortment of rounds that some manufacturers have started marking the lower receiver “Multi” or “Multi Cal.”
This is no specialization: your box stock 5.56mm AR-15 from most makers can, with as little as a change of the barrel and magazine, chamber an entirely new cartridge, the most famous and popular of these in the modern era being the .300 Blackout conversion.
Some guns can use alternate rounds effortlessly, load and go, while others take a little more work. But all of them offer the shooter a broader pool of available ammunition to draw from, as well as a different tool to solve different problems.
Why Go with a Multi-Caliber Gun?
It does not take much in the way of imagination to think of a scenario where a multi-caliber gun would be of use to a prepper, either during a SHTF incident or in kinder times.
The most common perk of a multi-caliber gun is coming up with an alternate ammo supply if your primary is exhausted. .357 Magnum users who have run out of full-house magnum loads will be thankful they can get cheaper .38 Special and keep on trucking.
A user of the same gun may appreciate dialing down the power if they are loaning the gun to a less-skilled relative or friend. Or they may simply get more from high-volume practice sessions or training by shooting the far milder .38 Special before confirming their skills with the .357 and carrying it loaded accordingly.
A multi-caliber rifle ala the AR can give you a tremendous amount of flexibility with a minimum amount of fuss, allowing you to go all the way from a .22 LR up through intermediate .270 and .30 caliber rounds before topping out at positively stomping .450’s. All easily accomplished with an upper receiver and magazine switch.
While most will have no call for this amount of variety, the flexibility opens up some attractive tactical possibilities, giving you the option to go from an all-around capable 5.56mm carbine to a deadly-quiet short barreled .300 Blk by swapping out an upper and magazine.
A couple of pins, a fresh mag, and you have reduced your signature to almost nothing. Another example using the same setup would be a 5.56mm to 6.5mm or 6.8mm conversion configured as a precision rifle to extend your range and afford more power.
In the case of the latter, an optic can be pre-attached and zeroed on the barreled upper receiver, and barring some significant damage to the lower will be expected to maintain that zero when detached from the lower receiver.
Compared to toting multiple rifles for different purposes, this eases logistical concerns and saves weight. Always worthy of consideration for any prepper, but especially those on the move or with limited cargo room.
Is Multi-Caliber Capability Worth Sacrificing For?
That is a question with many variables, and the answer depends mostly on your objectives and personal preferences. Some multi-cal guns don’t “cost” you anything since they can innately chamber an alternate round, good examples being the .357 Magnum mentioned above, but also .44 Magnum and its smaller .44 Special cousin, as well as the .327 Federal Magnum being able to chamber three alternate and smaller .32 rounds, though all of them are pretty rare today.
If you are already relying on or plan to rely on a double-action .357 as your defensive handgun, this is a no-brainer and indeed this capability is free and comes with no additional downsides except the warning to watch your chambers for lead buildup if shooting a steady diet of .38 Special.
For someone keeping a brace of handguns available for family or survival group usage, revolvers make excellent “handouts” to those who are not as well-trained or as practiced as shooters.
Turning down the power level from .357 Magnum, which ranges from brisk to violent, to a more sedate and manageable but still effective .38 Special is an excellent capability for a “mixed skills group” to have.
You could even keep some truly powder-puff loads available (like .38 wadcutters) for grandma and grandpa to make use of if needed. The most efficient and dedicated shooters may scoff at sacrificing so much raw effectiveness at the altar of convenience and adaptability, but remember there are good people out there who will need your help, and you may not have any time whatsoever to bring them up to speed on a more complex or difficult to shoot gun.
Moving up a peg on the conversion difficulty scale is a handgun that might need minimal modification to chamber a new cartridge. One such arrangement that comes to mind is a revolver that is convertible from .22 LR to .22 Magnum.
You may scoff at the idea of a .22 LR being a dedicated survival gun, but I have written about the concept several times and think it has tremendous merit. I especially like the idea of being able to “punch up” with the .22 WMR for easier hunting of more serious game.
You can do a lot with a .22 LR, if you are good, but the most hot-rodded .22 LR load is nowhere close to the performance of a .22 Magnum and don’t kid yourself that it is.
Not all will have need of this capability, but for those who do, a spare cylinder, small box of (still light and tiny) ammunition and a miniature red dot makes for a low-cost, low-weight hunting rig. Worth including if you plan to be out a while, if you ask me.
A similar outcome can be achieved for semi-auto users with a Glock 20 in 10mm Auto converted down to .40 S&W with nothing more than a barrel change.
Yes, the .40 S&W will load and feed normally from Glock 20 magazines (As an aside, my own testing with such a configuration using a high quality KKM barrel was surprisingly reliable, even when the oversized magazines were loaded with .40 in a deliberately haphazard way).
The 10mm Auto is generally considered “overkill” and inefficient for self-defense use against humans, but when stoked with top-end rounds is highly capable as a hunting round.
For those who would like a viable hunting arm in addition to one more or less optimal for defense, this is a similar multi-cal arrangement to a .22 LR/.22 Mag in a revolver: minimal parts for a major performance gain.
Other options like caliber swapping an AR may be worth it if you prepare for a specific application that it can better fill compared to lugging another gun around, but AR caliber changes have varying levels of hardware commitment.
On the low end, you can simply switch the barrel and (ideally) the magazine out on for a .300 Blackout conversion, but this will require a dedicated bench setup to achieve.
Most users seeking to swap AR calibers do so with an entire, complete and dedicated upper receiver assembly for the purpose. While smaller and lighter than a second rifle, these items weigh several pounds before you tally the weight of ammo.
For someone hunkered down at home, not such a big deal. If you have to go mobile in a vehicle, you will be paying attention to all the cubic inches and pounds you are consuming from the vehicles internal and external cargo capacity.
If you are bugging out by foot, you will really be paying attention to every ounce added to your pack, at least you will if you know what is good for you. An entirely separate AR upper will gobble up quite a bit of room in your BOB.
Even then, it could make good sense if your BOL is a wide-open space that would be best serviced by a rifle with superior glass, range and power, compared to one optimized for short-range self-defense. Alternately, keeping your long-range upper and ammo pre-cached at your BOL waiting to hop on to your rifle you are carrying is another viable method.
Keep in mind, as you raise the level of material investment for a caliber swap, it gets expensive in cash, weight, and space. A complete upper receiver is less expensive than a commensurate quality complete rifle, but that cost is most of the cost of that complete rifle.
A quality spare barrel for a semi-auto is a significant fraction of the cost of a complete pistol. And so on and so on. Ammo too is no free lunch: any alternate ammunition that you carry “just in case” is weight and space not devoted toward your primary ammo.
Considering that there are guns in every class which are so good all around that they make specialized setups more or less irrelevant under most conditions, you should carefully assess the likelihood that you will need the capability a multi-caliber gun can offer you if it will require committing to toting extra parts around.
The 5 Best Multi-Caliber Guns for Preppers
Smith & Wesson 686, .357 Magnum, 4” bbl
My appreciation for S&W’s workhorse large frame .357 is well known. If you need a damn tough revolver that still shoots like a dream, look no further.
This essential multi-caliber wheelgun covers all the bases we want for a self-defense handgun while offering all the perks of secondary ammo selection we discussed earlier: reliable, durable, weather resistant, adequate caliber and easy to shoot well with just a little practice.
This is one multi-cal choice that will pay dividends before and during a SHTF event. .38 Specials are significantly cheaper than full-house .357 Mag, and allow you train cheaper and longer.
Aside from its hefty weight deducting half a point, this is the only thing keeping this from being the perfect gun to hand off to the less experienced shooters in your group, and it makes for a fine hunting arm capable of taking medium game when loaded with potent .357’s, to say nothing of its efficacy (and excellent historical record) against humans.
A new classic and a favorite.
Ruger Redhawk, .44 Magnum, 4” or 5.5” bbl.
For preppers who want portable firepower capable of bagging big game while still having some viability as a defensive arm, Ruger’s Redhawk is a good choice.
Certainly rugged enough to survive the End Times, this beefy wheelgun can be loaded down with .44 Specials (a highly potent self-defense round) when carried in anticipation of human predators, or stoked with the perennially stompy .44 Magnum for harvesting larger game at extended distances.
You can get better performance for both applications but especially for hunting by adding a compact optical base and an MRDS.
Big bore handguns typically fill the niche of specialist weapons for preppers, but this is one configuration that can work just fine as a defensive piece if, and it’s a big if, if you can afford to find, buy and store plenty of .44 Special ammo.
Not the most common round any more, and expensive. That makes this one setup that is a great choice for reloaders.
Smith & Wesson Model 48, .22 Magnum
.22 Mag/.22 LR convertible revolvers are by no means rare today, but the problem is you’ll find most of them in the single-action category. Sure, that’s cool if you are wandering the Mojave with your big iron on your hip, but savvy preppers will want something capable of immediate follow-up shots for self-defense.
This model is a vintage one that you’ll need to search for, but if you are lucky enough to have one they can be converted to .22 LR by pulling one screw and swapping the cylinder.
Ideal for hunting small and even soft-skinned medium game with a well placed magnum, these are classic S&W through and through. High-quality, dependable and accurate.
If you were in love with the idea of a .22 Mag/.22 LR combo gun and cannot find one of these gems (or don’t want to shell out the coin), you might consider a Ruger Single-Six convertible instead. It is single action, and hardly ideal for defense, but still brings many of the same advantages to the table.
Glock 20, 10mm Auto
This is a sleeper combo and game-getter for semi-auto fans in the same way that the Redhawk is for wheelgun lovers up above. By dropping in a purpose-made .40 S&W conversion barrel, nothing more, you can convert your big 10mm into its smaller child cartridge, the .40 S&W.
10mm haters out there are already snickering to themselves that they are the same thing, but 10mm disciples know they are not.
The modern state of the 10mm round, resurgence and all, still sees it largely neutered in most factory ammo loadings. Loads near the top of the performance spectrum bring it to within a good toss of the .41 Magnum, though that cult classic proper magnum still has a significant edge over even the hottest 10mm.
Nonetheless, a 10mm with appropriate projectile is capable of taking most animals on the North American continent with aplomb. Compared to a similar revolver, you will be packing in 15 badass pills in a quickly replaceable magazine. That is worth some comfort when after dangerous quarry.
As a .40, the Glock 20 frame is oversized, thick and slightly cumbersome, though the newest generations and SF models alleviate the worst of this.
This is not a conversion the factory would approve of, but my own testing along with other interested parties in the concept has shown me everything I need to know about the reliability and viability of the .40 in this platform. No new mags, or springs, required. Just the barrel.
Another cool combo for those who fancy taking larger game with their handguns, and far more suitable for defense against people (in either chambering) than a big .44 revolver.
AR-15, 5.56mm (nominal)
With the AR, the sky is the limit, almost, on caliber conversions. You can take your box stock 5.56 mm AR all the way down to a 9mm, even a .22 LR is you want to. You could take it up to a .450 Bushmaster or .458 SOCOM for major performance against big critters or major obstructions. You are limited only by your budget and space allowances.
Depending on your desired conversion and own plans, you might be able to get by with a barrel, bolt, and magazine, or some combination thereof. Anyone who does not want to wrench on their guns will simply have a complete upper receiver ready to drop on, load and roll out with.
While this level of modularity is appealing, and even a bit dizzying, it is not all sunshine and rainbows on the wonderful world of AR caliber conversions.
Some swaps are more logistically viable than others, needing only, effectively a new barrel to effect, but these come with their own perils. The .300 Blackout is one such excellent special purpose cartridge that comes to mind.
Plainly states, the .300 Blackout is 100% capable of chambering and firing in a stock 5.56mm rifle. But just because it can fire does not mean the .30 caliber bullet can fit down the tiny .22 caliber barrel.
The result is a spectacular and dangerous kaboom of the highest order. These are catastrophic events that utterly destroy a rifle and seriously imperil the shooter.
If you are planning to “cross-pollinate” these two calibers, you must have rigid and strict controls in place to completely eliminate the chances that any .300 rounds could find their way into a 5.56mm gun. Easier said than done when these cartridges are designed to share magazines…
Even with these warts, the ability to so wildly alter the performance characteristics of a rifle without committing to the bulk of a separate gun is something worth thinking about, at least for some preppers.
Multi-caliber guns can solve problems in ways that other guns cannot, all for a minimal expenditure of funds or space. While not every situation calls for the capability and not every prepper will have need of them, multi-caliber guns do make sense so long as you can still fulfill your objectives with their default chambering.
Just like having a multi-tool or Swiss Army knife can take the place of a larger, heavier toolbox, these multi-caliber guns can take the place of an armory in the right circumstances.