There have been dozens of articles on survival firearms on SurvivalBlog, and many of them focus on the “bare minimum” and/or doing the most with the fewest firearms. None of us wants to fall into the trap of over-emphasizing firearms at the expense of food, water, arable land, and other supplies for balanced preparation. We all know of “that guy” with 100 guns and a case of MREs who considers himself prepared for anything. This is especially important when you’re looking to bug out WTSHTF; it’s very difficult to reconcile leaving firearms behind and, say, 50 long guns + 50 handguns + ammo & accessories can easily fill a truck all by themselves.
I wanted to focus on firearms that can either fire multiple calibers without modification or with fairly minor modification --- no unscrewing of barrels with special spanner wrenches, etc. There are two purposes behind multi-caliber guns (or MCGs) for the prepper: to increase the flexibility of the firearm to use found or bartered ammo, and to increase the utility of the firearm (reduced recoil, hunting a larger variety of animals, etc). The big reason behind most of these for the non-prepper is cost of shooting, which is related to the prepper concern of cost of stockpiling.
I am splitting MCGs into two categories, those that require no modification and those that do. Some of these are basic knowledge to old hat gun nuts, but talk to any gun store employee and they will tell you there is no such thing as “common knowledge” when it comes to guns.
If I get anything wrong please let me know! I’ve shot plenty of these but far from all, a lot of this is research. If in doubt, read the manual that comes with the gun, manufacturers are getting quite savvy at covering their butts with warnings against cartridges that will chamber but aren’t meant for the gun.
MCGs not requiring modification:
Most MCGs that don’t require modification to shoot multiple calibers typically just fire cartridges of the same bore diameter but differing power. Less powerful cartridges are often cheaper and put far less stress on the weapon (increased longevity). I list the longest cartridge first.
.22 Long Rifle (LR) / .22 Long / .22 Short: Nearly all revolvers and tube-fed, non semi-auto (bolt, level, pump) rifles that fire .22 Long Rifle will fire their older, weaker .22 Long and .22 Short cartridges just fine. Semi autos designed for the .22 LR won’t cycle these weaker cartridges but can be used as a single shot. The utility is questionable as .22 Long and .22 Short are much, much less common than .22 LR. .22 Short is fine for pest control in built-up areas but in a true grid-down SHTF scenario I think subsonic .22 LR will be much, much more useful. Also, the shorter cased .22 Long and .22 Short can build up lead in the chamber (making shooting .22 LR difficult until cleaned) and worse, with continued use can fire-cut the chamber directly in front of the case and ruin it for .22 LR shooting.
***I am not aware of a single firearm that can safely and accurately shoot .22 LR and .22 Magnum (also called .22 WMR) without modification due to the wider case of the .22 Magnum. .22 Magnum won’t chamber in a .22 LR gun, and while .22 LR will slip just fine into a .22 Magnum chamber, it will cause split cases, jammed cylinders, and other problems. There are a number of revolvers that can shoot both with a cylinder change that I’ll dig into later in the article.
.357 Magnum / .38 Special: Probably the most common MCG combination. Any .357 Magnum revolver and lever / pump action rifle will fire .38 Special. Both are extremely common. From a prepper standpoint, I believe one should always get a .357 Magnum versus a .38 Special gun, it’s going to be built much stronger, fires both rounds, and will be just a fraction heavier / larger. Most .357 Magnum semi autos will not cycle with .38 Specials. The newer Coonan Arms .357 Magnum pistols are built to use .38 Specials with a special weaker recoil spring.
The most unique variant of the .357 Magnum MCG is definitely the Phillips & Rodgers Model 47 Medusa revolver. These were low-production in the late 1990s and are exceedingly hard to find and expensive when you do run across one. They were designed to fire just about any non-bottlenecked pistol bullet (rimmed or not) in the .355-.357 bullet diameter range. This is 25+ cartridges and includes the .38 Special, .357 Magnum, .380, 9x19mm, .38 Super, etc. They are still in use by the Navy SEALs as they can be fired underwater. I consider this the ultimate long-term SHTF centerfire handgun, although parts are hard to stock up and a single gun might run you $1500 or more.
.44 Magnum / .44 Special: Pretty much the same dynamic as the .357 Magnum / .38 Special, although .44 Special isn’t very common and not a discount from “Wal-Mart” .44 Magnum for the shooter/stockpiler. .44 Special is much more tolerable and easy to shoot than full-bore .44 Magnum loads if you’re considering how to arm your less gun-savvy or smaller-statured friends WTSHTF. The only .44 Magnum semi-auto pistol I’m aware of, the Desert Eagle, won’t cycle .44 Special.
.327 Magnum / .32 H&R Magnum / .32 S&W Long revolvers: The new .327 Magnum will fire all three while the .32 H&R Magnum can also fire the .32 S&W Long. None are very common, the main selling point of the .327 Magnum is that the guns typically hold 6 cartridges versus a snub nose .38 Special or .357 Magnum that holds 5. Not much SHTF utility here.
.410 bore / .454 Casull / .45 Colt: There has been a recent crop of .45 Colt revolvers that can also fire .410 bore shotgun shells (Taurus / Rossi Judge series, S&W Governor, etc). I’ve had the pleasure of shooting an early Judge and think it’s a great pest control gun but fail to see the utility in it WTSHTF. Perhaps more useful are .454 Casull / .45 Colt revolvers as the .454 can be used on medium to large game along with predator protection while the .45 Colt is a better fit for self defense against two legged varmints. If you’re convinced you need a shotgun revolver, get a S&W Governor as it will fire .45 ACP as well, kind of a poor man’s Medusa in .45. The Taurus Raging Judge will fire .410, .454, and .45 Colt but is a big handgun and weighs more than 4 pounds, empty!
While any .454 Casull will fire .45 Colt, don’t try .454 Casull or .45 Colt in any .410 bore shotgun unless it explicitly calls for it. A good rule is any smoothbore .410 shotgun is only designed for .410 shotgun shells; you’re not going to hit anything smaller than a bus with a .45 Colt out of a smoothbore, and a .454 Casull round just might blow your gun/face up. (It has five times the maximum pressure of a .410 shotgun shell).
MCGs requiring modification:
The sky is the limit with MCGs that require some modification to shoot additional calibers. New cylinders, barrels, upper receivers, etc turn one firearm into two or more.
.22 Long Rifle conversion kits for semi-auto pistols and rifles: This is such a great concept that nearly every popular centerfire pistol and rifle has a conversion kit. Originally popular with military forces for cheap target practice, this has bled over into the civilian shooting community that likes cheap practice too. For the prepper, this allows one to use one gun for defense / big game hunting and quickly convert to hunt small game. Also, one can easily and inexpensively stockpile tens of thousands of .22 LR, in a long term SHTF scenario you can keep your guns running longer. I’d sure rather have a Model 1911 in .22LR versus a butcher knife spear for example. Below I have listed some common guns that have kits available.
ARs chambered for 5.56x45mm / .223
Mini-14s chambered for 5.56x45mm / .223
AKs chambered for 7.62x39mm
FAL and clones
G3/HK91 and clones
HK93/33 and clones
Beretta/Taurus 92-style pistols
SIG-Sauer P series
.22 Long Rifle / .22 Magnum switch-cylinder revolvers: These are revolvers that will shoot both calibers with a simple spare cylinder. The most common is the well-made Ruger Single Six Convertible. Harrington & Richardson makes a cheaper knockoff that lacks the transfer bar safety and polish of the Ruger. Great utility to use two very common cartridges.
.357 Magnum or .38 Special / 9x19mm switch-cylinder revolvers: Perhaps less well known are the switch cylinder .357 Magnums to fire 9x19mm (although more common in Europe). Ruger makes a convertible Blackhawk single action.
.45 Colt / .45 ACP switch-cylinder revolvers: Ruger also makes a Blackhawk convertible for these two calibers.
Rossi Wizard Series: A couple of years ago Rossi came out with a line of single shot long guns that, with a barrel change, could convert to a large selection of rimfire, centerfire, muzzleloader, and shotgun cartridges. Now one rifle could be an inexpensive .22 LR, a deer-slaying .30-06, a muzzleloader for that hunting season, and a 12g shotgun for birds --- or anything in between. Of course, the drawback is it’s a single shot, but the utility is hard to ignore, especially the youth models. Find out what the most popular calibers are in your area and get a Wizard with those barrels just in case.
7.62x25mm Tokarev / 9x19mm switch-barrel conversions: Although they can be tough to find, most pistols in 7.62x25mm like the CZ-52 and Tokarev clones have had 9x19mm barrels made for them. Great way to make these handguns more useful in a SHTF scenario as 7.62x25mm isn’t all that common.
.40 S&W / .357 SIG switch-barrel conversions: Most popular pistols in either caliber have a barrel available for the other. If you have one, get the barrel for the other caliber.
I am aware of switch barrels to convert Glocks and SIGs in .40 S&W or .357 SIG to 9x19mm, not sure if there is another pistol this conversion is available for.
10mm / 9x25mm Dillon switch-barrel conversions: There are 9x25mmD barrels available for 1911s and Glock 20 pistols (perhaps others but I’m not aware of them). 9x25mmD was designed for competition shooting and produces enormous flash and noise. It does not have much SHTF utility, in my view.
In addition to 9x25mm Dillon, there are switch barrels for the 10mm Glock 20 for .40 S&W, .357 SIG, and even special order .38 Super (these are NOT the same as the stock Glock barrels for their respective models but are special fit for the Glock 20). The Glock 20 is a pretty amazing gun that can fire 5 calibers with a barrel change and has a .22 LR conversion kit too. And, since it shares the same frame as the .45 ACP Glock 21, you could get a complete .45 ACP slide & barrel for your Glock 20 to make it a Glock 21 (and then, naturally, get a .400 Cor-Bon barrel for it, see below). Or go the other way and start with a Glock 21 and get all the Glock 20 stuff. Great pistols, not a huge surprise they are so popular. Apologize if anyone went cross-eyed trying to follow this explanation!
.45 ACP / .400 Cor-Bon switch-barrel conversions: Many pistols chambered for .45 ACP have .400 Cor-Bon barrels available. Most of the time these don’t require a new recoil spring. The .400 Cor-Bon is a poor man’s 10mm and is simply a .45 ACP necked down to a .400/10mm bullet. .400 Cor-Bon never gained much popularity, but there are some that convert their .45 ACP to a 6” barrel .400 Cor-Bon for hunting and predator defense. For preppers, not sure it’s truly worth the money unless you want one handgun for human and predator defense.
SIG P250 Pistols: The P250 is a pistol from SIG that can change calibers (.22 LR, 9x19mm, .357 SIG, .40 S&W, .45 ACP) by changing the slide and barrel assembly (and magazines) much like an AR upper. More expensive than, say, a Glock 22 with a .40 S&W, .357 SIG, and 9x19 barrels but throw in the .45 ACP which a .40 S&W Glock can’t do. With all of the kits you have a handgun that covers almost every common pistol caliber. I’d still rather have a Glock 20/21 will all the accessories as described above.
The less common EAA Witness full sized pistols can switch between .22 LR, 9x19mm, .38 Super, .40 S&W, .357 SIG, 10mm, and .45 ACP by changing the slide assembly and magazine. Each kit is about $200.
AR Upper Receivers: I saved the best for last, this is where most of the MCG action has been in the last 10+ years. An entire new family of cartridges has been created around the constraint of the AR-15 magazine well width and AR-10 cartridges like the .243 Winchester have gained popularity as well. Buying an upper is almost always going to be less expensive than a complete rifle, and if you put a lot of money into a lower with an aftermarket trigger, high-end stock, and grip why not stretch that out to several platforms? Of course, the big drawback is one lower, one shooter --- bad if you need to defend your retreat and none of your buddies bring a rifle. Some may come to the conclusion that 2-3 complete ARs are better than one lower and 5 uppers. If you’re going to make the leap, I am of the opinion that a 5.56x45mm base rifle + pistol caliber matching your sidearm + 6.5 Grendel long barrel with scope + .22 LR conversion kit would be the most effective and efficient setup. Note that, even pinching pennies with lower end upper assemblies, this will be almost $3,000 before optics. For $2,500 you could buy a basic AR, an inexpensive pistol carbine like a Hi-Point or Kel-Tec SUB2000, a budget long range .308 bolt action rifle, and a .22 LR kit for your AR (or basic Ruger 10/22 rifle) and have 3-4 complete guns. It’s not for everyone and your mileage may vary. I honestly don’t see much utility in multiple uppers for AR-10s as, beyond .308 and .243, the cartridges are just not all that common.
Now, the newly announced Colt CM-901, with its lower receiver that can adapt to both AR-15 and AR-10 size uppers, will be a great SHTF platform if it works as advertised. You could have a CQB 5.56mm carbine and a long range .308 in one platform.
Upper calibers for AR-15 type guns (available non-custom):
5.56x45mm / .223 (of course)
.22 Long Rifle (although the conversion kits are going to be cheaper by a long shot)
5.45x39mm (super cheap surplus ammo but filthy and often corrosively primed!)
6.5 Grendel (great long range cartridge)
.300 AAC Blackout (great for suppressed rifles)
9x19mm (also great for suppressed rifles)
.30 Remington AR
.243 WSSM (Olympic Arms)
.25 WSSM (Olympic Arms)
.300 OSSM (Olympic Arms)
.50 BMG single shot (not sure how great these are, but they’re available)
Upper calibers for AR-10 type guns (not all are current production):
7.62x51mm / .308 Winchester (of course)
Entire WSM family
Entire SAUM family
I hope this detailed look into multi-caliber guns gives good food for thought, especially if you’re looking to build a small battery of flexible SHTF firearms that’s highly portable versus a huge, difficult to move stockpile at your permanent live-in retreat.