about caliber conversions

Caliber Conversions - Good Reason To Buy a .40 Caliber Gun?


There's an aspect of the .40 caliber platform that can get ignored, namely that of caliber conversion. Most people wouldn't think of it, though there are some good reasons for it. Why do that if you can just buy one gun in the right caliber?


Or, for that matter, why not just buy more than one pistol? Once you have one, you're gonna want more. However, switching calibers can give you some real versatility with a carry gun or range gun, so it's something that some people might look into.


Not Every Handgun Suited To Caliber Conversions


Caliber Conversions 40 cal to 9mm

It should be noted that not every gun is suited to a caliber conversion. The procedure is really only suited for semi-autos as converting a revolver is the equivalent of major surgery; converting a semi-auto is more like an outpatient procedure. For a revolver, the barrel has to be bored out, as must the cylinder - though in some instances, the cylinder can be replaced with one of the correct chambering.


Converting a semi-auto, on the other hand, is potentially - depending on the pistol - very easy. Provided a suitable pistol, just drop in a barrel for the caliber you want and use the appropriate magazines. Some barrels may require some minor fitting but and some plug and play.In some cases, you may also need to swap the extractor.


That said, not every caliber conversion is that easy. Converting a pistol to 9mm from .45 ACP, for instance, is going to be more complicated - barrel, recoil spring and extractor at minimum, possibly a different firing pin depending - and so on.


Pistols chambered in .40 S&W are ideally suited to certain cartridge conversions. Since the .40 S&W was designed for use in a 9mm frame, switching to 9mm is (usually) easy, as is converting to .357 Sig.


40 To 9mm Conversion Can Save Money At The Range


Why bother with a 9mm conversion when you can just buy a 9mm to begin with?



Well, because you can do your range work for cheaper and then carry the larger round for defense, which some prefer. It's not uncommon; after all, how many people over the years carried .357 Magnum but did most of their range work with .38 Special?


A good number of people still do.


By converting by 9mm, you can do more shooting for cheaper. Though .40 S&W is only marginally more expensive than 9mm, it can add up. Let's say you shoot 200 rounds a month and can save $2.50 per month shooting 9mm instead of .40 S&W. That's $30 in savings per year - not much - but over a 10 year period starts to add up.


It can also save some wear and tear, though what you hear about .40s wearing out quicker has some truth to it but also a lot of bunk. The two rounds have virtually identical chamber pressures and the recoil force isn't so much more that the .40 will wear out a frame or barrel too quickly.


Most people won't shoot enough rounds in their lifetime to wear out a .40 or for that matter a .357 Sig. If you're putting a few hundred rounds through it per week, then maybe...after a decade or two. However, you can enjoy the softer-shooting round for practice and use the larger for carry.


Since .40 S&W and .357 Sig have identical case diameters, .357 Sig conversions are very easy indeed, as only a drop-in barrel is usually necessary. (The magazines will still work.) However, given the higher chamber pressures developed by the .357 Sig, a stiffer recoil spring is usually in order as well.


Why Bother With A Cartridge Conversion?


caliber conversion kits save money

Why, indeed, bother with a cartridge conversion when you can just buy one caliber and learn to shoot it well? It's a perfectly valid idea; after all, the caliber wars are mostly bunk and really the best pistol to put in a holster and strap on with a gun belt is the one you shoot best.


Variety is the spice of life, and some people like multiple calibers. There are, though, some advantages that some calibers confer. For instance. .40 S&W can pack slightly more punch than 9mm and some loadings expand more and more reliably than some 9mm loadings. More so with .357 Sig, as the round was devised to replicate a 125-grain .357 Magnum round.


Why would that matter? You can carry 9mm for warm weather, and either .40 or .357 Sig during winter, as some people like to go up a caliber during the cold months. Additionally, you can carry .357 Sig in the woods as a backup.




Sam Hoober 

About The Author


Born in southeastern Washington State, Sam Hoober graduated in 2011 from Eastern Washington University. He resides in the great Inland Northwest, with his wife and child. His varied interests and hobbies include camping, fishing, hunting, and spending time at the gun range as often as possible.

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