The first time I saw a widely advertised caliber conversion for a firearm was the SIG P250. I was enamored by the gun and the idea that I could easily and quickly change calibers without the need to do an FFL transfer. This seemed too good to be true. The SIG P250 wasn’t a success by any means, but it did bring us the P320, which maintained the caliber conversion and size conversion features.
SIG became a champion of the caliber conversion idea. They sold the MCX and MPX on the idea of easily converting the guns to various calibers and barrel lengths. When we talk caliber conversions, we aren’t discussing something like swapping complete uppers on an AR. Instead, we are discussing designs that promise to make it both easy and affordable. It’s often promised to be as easy as swapping barrels and maybe a bolt, and doing so isn’t difficult.
Admittedly, swapping calibers on an AR isn’t all that hard, but it was never the purpose of the design. Even so, the AR design is probably the most successful of any caliber converting rifle. With that in mind, rifles that promise caliber conversions rarely work out, and it’s both a mixture of the people buying the guns and the industry failing to support the concept once the end user purchased it. Let’s examine why these things never succeed.
Three Reasons Why Caliber Conversions Fail
The idea for this article came up because I think the PWS URX is so flipping cool. I saw it at SHOT last year, and it seems to be shipping as we speak. When I went to search for caliber conversions, which are the main bread and butter, I noticed none were on the market yet. You can get the rifles, but you can’t get the conversions easily. It made me dive through the modern history of caliber conversions and uncover why they never work.
Caliber Conversions Are Too Expensive
First and foremost, when caliber conversions actually hit the market, they are often extremely expensive for what they are. Take, for example, the SIG MCX promised and delivered caliber conversions. A SIG MCX costs around two thousand dollars, a hefty sum, to be sure. How much would converting my 5.56 MCX to a different caliber cost me?
Depending on the caliber, it can cost anywhere from $600 to $1,100. The conversion costs half as much as the original rifle at times. Switching from 5.56 to .300 Blackout is cheap because it’s just a barrel swap to 7.62×39. It gets a bit pricier due to the new bolt and magazine required.
What about the P320? Let’s say I want to convert it to .40 S&W. The caliber Xchange kit costs $429.99. If I shop around, I can buy a new P320 for less than that. It’s just costly to swap calibers, and you might as well buy an entirely new gun.
They Rarely Materialize
One thing that hurts early adopters is when companies promise conversions, but they never come. Let’s pick on SIG again. They introduced the MCX in 9mm with promises for .40 S&W and .357 SIG conversions. Those conversions never materialized—and MCX owners were stuck with their 9mm guns.
The same goes for the ACR from Bushmaster. Well, Remington and Bushmaster have never introduced conversion kits, but a company called Templar Precision introduced caliber conversions a decade or so later. If you buy a gun without the caliber conversions available, be prepared for them to never appear.
No One Wants Them
This is the biggest one. People typically buy a rifle, PCC, or handgun in the caliber they want it to be in. Rarely does someone want to convert their rifle or handgun to another caliber. I know SIG promised the MPX in various calibers, but does anyone realy want a .40 S&W or .357 SIG PCC?
The same goes for handguns in 2024. The little 9mm round works, and no one wants .40 S&W and .357 SIG, so no one is buying SIG’s conversions. I think the most valuable conversions would be something drastic. A swap from 5.56 to 6.5 Creedmoor would be valuable, but who cares about 5.56 to 6.8 SPC? The same goes from 9mm to 10mm, rather than .40 S&W.
I think the PWS URX might succeed just due to that factor. You can swap from 5.56 to .308 or 8.6 Blackout fairly easily.
Caliber Conversions and You
Will these things ever work? Who knows. Part of them wants them to, but I can’t help but think they will always be too expensive to be truly successful. Maybe the SIG Twosome kit wasn’t a terrible idea? Package a gun and its conversion together to create a radical, easily convertible platform. That’s my idea, but I’m not a marketing pro by any means.
