So you’ve kinda figured out what kind of firearm you’re wanting to look at for your first handgun purchase, awesome! The next big question is…what caliber? Caliber debates are something that ignite all out wars on social media, so chances are you’ll never gain a whole lot of good advice on which one to go with.

In this guide I will be going over several calibers that you have probably heard of and breaking down some of the pros and cons of each of them. Of course, this is just to get you headed in the right direction in terms of what to pick out for your own use.

To get started I want to run through a handful of calibers that aren’t going to get mentioned and explain why.

  1. 10mm: 10mm is a fantastic caliber, it has a lot of energy, it pushes heavy projectiles fast, and it performs well in testing. However, your common plinking ammo is going to be expensive and only charged to .40S&W power levels. With there being so few platforms for the caliber and with the plinking/defensive ammo being so expensive I don’t see this as a viable beginner’s caliber. *duty caliber
  2. .357 Sig: I think bottleneck cartridges need to make a comeback, honestly. That said, the testing I have seen for .357 Sig has shown some inconsistent results in terms of both penetration and expansion with factory loadings. The same results have shown similar permanent wound channels compared to .40S&W and 9mm.
    Beyond this and aside from conversions, I would say there are even fewer handguns chambered in this caliber than 10mm. Ammunition is also in the same ballpark in terms of price and from my experience can be harder to track down. *duty caliber
  3. .45 Long Colt, .45LC: .45LC isn’t a bad caliber. But… there are limited platforms in the caliber and there aren’t many decent defensive loadings on the market. Beyond that, .45 Long Colt will be more expensive to plink/train with than the revolver calibers I’ll be diving into. In my experience, it can also be a pain to find in stock locally.
  4. .32ACP, 32 Automatic Colt Pistol, .32 Auto: .32ACP is really a dying caliber, there are very few options on the market, performance is typically dismal, and ammo can be expensive (as well as spare parts for the guns!) *mouse caliber 
  5. .25ACP, 25 Automatic Colt Pistol, 25 Auto: 25ACP is even more of a dead caliber than .32ACP and performs even worse. On top of this 25 Auto has even fewer defensive loadings (if any) available on the market. The primary reason you will see .25Auto guns being discussed is for the collector’s value of the old vest guns.
    Side Note: If you go against my advice and go with .32ACP or .25ACP, I would recommend using quality ball ammunition for defensive purposes.
    For the other calibers above, I have not dedicated the time to researching good defensive options with them. 

With the calibers we’re ignoring out of the way, lets get into the more common calibers that a new enthusiast like yourself might be looking into. I’ll be separating this part into two categories. “Mouse calibers” and “Duty calibers”.

What differentiates mouse from duty calibers? Their overall effectiveness and tested performance. At the end of this portion of the caliber’s guide, I will explain the FBI protocols, how they affect you, and how I interpret the results in order to make my decisions on what rounds I carry.

Mouse Calibers

.22lr, .22 Long Rifle, .22 Rimfire: 22lr is really a caliber that is best saved for target shooting and pest control. The only real exception is if you suffer some form of medical condition that prevents you from shooting larger calibers such as arthritis.

Of course, carrying a .22lr is better than carrying nothing, but understand the limitations of the caliber. There are many instances of individuals attempting suicide via shooting at their temple with a .22lr and surviving. Rimfire cartridges are also less reliable compared to centerfire cartridges, especially in magazines which is why most of them are single stack. With magazine fed rimfired guns you run the chance of getting “rim lock”. Short and sweet on rim lock: Rim of one round jumps above/below another rim and seizes up the magazine.

When it comes to effectiveness .22lr is a peashooter…or less than efficient at stopping dedicated attackers. Temporary and permanent would channels are minuscule and getting proper penetration can be difficult for the caliber out of handguns.

Two new guns at two price points I would recommend checking out: Charter Arms PathfinderRuger SP101

If you are needing to use a .22lr as your primary carry weapon 40gr CCI Velocitors (Ideally use these in a 4-6” barrel for best results) or higher velocity FMJ. 

Pros: Cheap to buy, no recoil | Cons: Finnicky semi-autos (reliability wise), rimfire, inadequate wounding capabilities.

.22WMR, .22Mag, .22 Remington Magnum, .22 Magnum: As you can probably tell by the name, .22Mag is essentially the better performing .22lr. Whereas .22magnum is still a rimfire cartridge, it does perform a lot better than .22lr. If you’re running a shorter barreled handgun, such as a snub-nosed revolver, I would strongly recommend going with the .22Mag over .22lr.

Recoil is still near non-existent but you get improved performance over the .22lr cartridge. Performance wise for a small, low-recoiling caliber .22Mag doesn’t do a horrific job in terms of wounding capabilities…but it isn’t exactly good. The wound channels both temporary and permanent aren’t necessarily anything incredible, but with the right defensive rounds penetration is at the very least adequate.

Two new guns at two price points I would recommend checking out: Smith & Wesson 351PD, Charter Arms Pathfinder

The defensive ammunition that I would recommend: 40gr Speer Gold Dots or quality higher velocity FMJ.

Pros: Low recoil, better performance than .22lr, Ammunition is typically made to a better standard | Cons: Ammo cost is close to 9mm, Finnicky in semi-autos, rimfire

.380ACP, 9mm Kurz, 9mm Short, .380 Auto, .380 Automatic Colt Pistol: .380ACP is the only center fired mouse caliber that I will be going over right now. From my understanding John M. Browning designed the .380ACP to perform like .45ACP but out of the old vest pocket guns that were ever popular in the era.

Recoil is going to be substantially more than either of the above out of similarly sized platforms. But it’s going to be less than 9mm out of similarly sized platforms. Reliability is also going to be better because it’s centerfired versus rimfired with the latter.

Performance wise, .380ACP does a decent job with specific defensive rounds, but with anything less you’re better off carrying quality ball ammunition. Adequate penetration is something that .380 can struggle to obtain and wound channels aren’t as expansive as any of the duty calibers.

Three new guns at three price points I would recommend checking out: Walther PPK, Glock 42, Ruger LCP II. Honorable Mention: Smith & Wesson E-Z .380; I don’t like grip safeties and don’t like recommending guns with them. but the E-Z is an excellent option for those with medical conditions.

The defensive ammunitions that I would recommend are: Corbon 70gr PowRball, Hornady 90gr FTX Critical Defense, Sig Sauer 90gr V-Crown, and Underwood/Lehigh Xtreme Penetrators

Pros: Less recoil than 9mm in similar platforms, centerfire | Cons: Expensive plinking ammunition, Poor penetration capabilities (typically)

Duty Calibers

Now we can dive into the calibers that meet the minimum standards set by the FBI’s defensive ammunition protocol. After I get done going over these calibers, I will explain what the FBI’s protocol’s are and why they are important to you.

9mm, 9mm NATO, 9×19 NATO, 9×19, 9mm Parabellum, 9×19 Parabellum: 9mm has come a long way in terms of bullet technology since it was first widely adopted. Today 9mm is seen as one of, if not the most, versatile caliber on the market. Guns chambered in the caliber range from being as small as a Ruger LCP II with the Sig 938 all the way up to full sized 1911’s. The smaller they are, the easier they are to conceal, and even out of shorter barrels perform better than .380ACP.

That said, the smaller the 9mm, the more felt recoil and more muzzle rise you’re going to get. After going over the 3 duty calibers, I will be doing a small recoil profile for you from my experience with them. Performance wise, 9mm is getting adequate penetration reliably, wound channels are within proximity to the width of .45ACP, and it can be argued that 9mm is the most reliable straight walled cartridge on the market.

Three Guns, Three Sizes, Three Price Points that I recommend checking out: Smith & Wesson Shield 2.0, Glock 19, CZ SP-01 Tactical

The defensive ammunitions that I would recommend are: Federal 124gr HST or Speer 124gr GoldDot.

Pros: Cheapest duty caliber to practice with, readily available defensive ammunition everywhere, passes FBI standards, highest capacity of the three duty calibers | Cons: Snappy recoil impulse, occasional issues against hard barriers

40cal, .40S&W, .40 Smith & Wesson: .40S&W used to be the king caliber…to some extent. The FBI originally requested a new caliber that resulted in the 10mm, the FBI adopted it, and shortly after abandoned it and adopted .40S&W. Why? Because their agents couldn’t handle the recoil of the 10mm…and the guns were having issues with the pressures.

If you are slightly recoil sensitive or don’t have the hand strength, .40S&W might not be for you. 40S&W does better through hard barriers when compared to 9mm, but the wound channels don’t offer much more over 9mm from what I’ve seen in all of the testing. In fact, the FBI in the last few years has switched back to 9mm citing seeing similar in their own testing results.

Three Guns, Three Sizes, three Price Points that I recommend checking out: Smith & Wesson Shield 2.0Heckler & Koch USP Compact, Glock 22

The defensive ammunitions that I would recommend are:  Federal 155gr HST, Winchester 180gr Ranger Bonded, Speer 165gr GoldDot

Pros: Lots of FBI certified defensive ammunition offerings, .40Cal guns tend to be cheaper, better performance through barriers | Cons: Snappy/heavy recoil, expensive plinking ammunition if not bulk ordered, lower capacity

.45ACP, .45 Auto, .45 Automatic Colt Pistol, .45Cal: .45ACP is an old caliber and was originally designed by John Moses Browning to be fired out of a 5” full size 1911. Today we still see it being used by a lot of police departments and a handful of militaries.

If you find either of the two duty calibers above to be too snappy, .45ACP is something that might be up your alley. There are a lot of people who hate the recoil impulses of the above, but love the recoil impulse of .45ACP. Out of the three, I do prefer the recoil impulse of .45ACP as long as it’s out of a compact or larger.

.45ACP is a reliable caliber but it does have some problems when it comes to defensive purposes. .45 ACP can have difficulties against hard and soft barriers (such as winter clothing) and achieving adequate penetration. Permanent wound channels are adequate when penetration depths are met.

Three Guns, Three Sizes, and Three Price Points I recommend checking out: Glock 30, Heckler & Koch USP Compact, Smith & Wesson M&P45 2.0

The defensive ammunitions I would recommend are: Winchester 230gr Ranger T, Remington 185gr Golden Sabre +P, Hornady 200gr XTP +P

Pros: Adequate wound channels, relaxed recoil impulse | Cons: Expensive ammunition, issues with penetration, the better defensive ammunition options are hard to find, lowest standard capacity of the 3 duty calibers

9mm Felt Recoil Impulse: Quick, Snappy, Light

.40S&W Felt Recoil Impulse: Quick, Snappy, Heavy

.45ACP Felt Recoil Impulse: Slow, Relaxed, Heavy


Revolvers are going to get their own little category for a couple of reasons. Their capacity drops them out of being in the duty category (in my opinion), but they aren’t exactly in the mouse caliber category.

There are a lot of revolver specific calibers on the market, I already mentioned .45 Long Colt in the introduction, but I will be focusing on .38 Special and .357 Magnum. These are the two most common revolver calibers and you can find both plinking and defensive ammunition easily.

.38 Special, .38Spl: .38 Special is in an age-old caliber that sits in an interesting spot. Performance wise it’s right between .380ACP and 9mm. I would say that recoil is pretty mild compared to 9mm out of a similarly sized pistol.

Performance wise .38 Special suffers from anything shorter than a 4” barrel. It doesn’t get to the velocities that it needs to expand reliably but it does seem to get to what the FBI has denoted as their preferred penetration depths between 14″ and 16”.

Three Guns, Three Sizes, Three Price Points that I recommend checking out: Smith & Wesson Bodyguard .38Spl, Ruger SP101Smith & Wesson Model 64

The defensive ammunitions that I would recommend are:  Federal 130gr HST Micro, Hornady 110gr FTX Critical Defense, Winchester 130gr Ranger Bonded +P

Pros: Soft-ish recoil, okay wounding capabilities | Cons: Expensive ammunition, difficulties with expanding (out of shorter barrels), difficulties with penetration (out of shorter barrels)

.357Mag, .357Magnum: .357 Magnum is to .38Special what .22Mag is to .22LR. Think of it as a super charged .38Special that came about due to the deficiencies of .38Spl. A big benefit being, .357 Magnum revolvers can shoot .38Special ammunition and can withstand .38Spl +P loads better than a .38Spl revolver rated for +P ammunition.

Recoil with .357 Magnum out of carry sized handguns (4” barrels or shorter) can be a handful. It’s rough and it has a snap to it. Penetration wise, .357 Magnum is going to have a much easier time than .38Special due to the charge pushing it forward. Permanent wound channels are also going to be substantially better than .38Special… and sometimes it bests all of the duty calibers I went over.

Three Guns, Three Sizes, Three Price Points that I recommend checking out: Kimber K6S, Ruger GP100, Smith & Wesson 686 Deluxe

The defensive ammunitions that I would recommend are:  Barnes 125gr Tac-XPD, Remington 158gr Semi-Jacketed Hollow Point, Federal 140gr Vital-Shok Barnes XPB

Pros: Fantastic wounding capabilities, .357 revolvers able to use .38Spl ammo, reliable expansion | Cons: Expensive ammunition, harsh recoil

Important Note: When looking at snub nosed revolvers, there’s two important factors that come into play. The first being control, the second being follow-up shots. Between .38Spl and .357 Magnum, the wound profiles out of both out of 2.5″ and shorter barrels aren’t substantial enough to justify the additional recoil and slower follow-up shots that .357 Magnum would deliver.

FBI Protocol's, Why they matter, and My recommendations

Now to explain the FBI’s protocols for testing ammunition and why they exist. The FBI Defensive Ammunition Protocols came to be due to the Miami-Dade shooting in 1986 that left officers and agents massacred. The FBI was extremely disappointed with the performance of the rounds used by law enforcement and their inability to stop the shooters.

The FBI uses 10% ordinance gel due to IWBA testing. The International Wound Ballistics Association did testing on anesthetized live pigs by shooting them in their hip while using high-speed X-Ray machines to capture what happened with various calibers. From this they calibrated their own gelatin to best mimic the results they saw in the pigs; their conclusion was that most similar acting media commonly available was 10% ordinance gel. 

The FBI’s requirements for defensive ammunition:
Ideal penetration between 14-16”, maximum penetration of 18”, and minimum of 12”.
Required depths based on shooting a person from the side (arm pit to arm pit)
These depths have to be achieved 5 times reliably through the following barriers:
No barrier, into gel.
4 layers of heavy denim (to simulate winter clothing) into gel.
Two pieces of 20ga steel (replicate the thinnest part of a car door) into gel.
Wallboard into gel.
Plywood into gel.
Windshield glass into gel.
The FBI also measures for:
Reliable Expansion
Retained Weight
Reliable Penetration

After the rounds are fired (30 total,5 for each test) they are extracted from each piece of gelatin, retained weight, penetration depth, and expansion widths are all recorded, and given a weighted score. Under penetration does give a bigger penalty than over penetration.

Why The FBI Testing Is Important

Police face the same threats that you and I do on a daily basis, the only difference is they’re arriving to your 911 call, and you’re the first on scene. Most Law Enforcement Agencies only use FBI approved defensive ammunition due to what happen in 1986.

Just because FBI approved ammunition is able to defeat the barriers in their testing protocol doesn’t mean that it will go through a person’s torso. In the last 5 years I’ve only seen one case of a total pass through with a handgun round. And that was a .45ACP FMJ bullet that went through a person’s tibia.

The approved ammunition has been tested to ensure that the user is getting the best performance out of their sidearm when going against a threat. Penetration and wound channels matter, a lot. With handguns you are relying on two things to stop a threat. Blood loss, or a CNS Shot.

What I Look For

Ideally, I look for 18-18.5” of penetration, the main reason being bone and fat. Ordnance gel only really accounts for muscle tissue, it doesn’t account for bone (obviously) or fat tissue. With a good concentration of training being on center mass, one of the big obstacles is the sternum, followed by the ribs.

I also look for uniformity in the rounds fired. If penetration isn’t consistent it’s immediately thrown out as an option for me, but I will still take into consideration a round that had 1 failure to expand.

My go to reference for defensive ammunition is the Lucky Gunner Labs. They do use clear ballistics gelatin in a controlled environment. The results may not be the same as with 10% ordinance gel but it is a good benchmark to use due to the consistency of testing protocols.

My Recommendations

Before I give my recs, I want to dispel a couple of myths before you set out deciding on what caliber you’re going to pick.
Myth Number 1: “Stopping power”. Duty calibers do not have the capability to reliably stop an attacker in one shot. Regardless of what anyone says, if a M193 bullet with 1,294 ft/lbs of energy doesn’t always stop a person with one shot, then one round of .45ACP with 580 ft/lbs of energy isn’t going to either. 

Myth Number 2: “.38Spl performs better than .357Mag out of shorter barrels.” This isn’t entirely a myth, but it’s more of an exaggeration. .357Mag does get better velocities than .38Spl out of shorter barrels, however, the wounding capabilities aren’t necessarily that much better. Once you take into account the additional recoil and slower follow up shots, it’s really a pick & choose situation.

Myth Number 3: “Energy Dump”. Energy dump is a term that’s misused to place .45ACP over 9mm (typically). I won’t get deep into it, but look at it this way. If a round “dumped all of its energy upon hitting the target” how is it going to penetrate? If it “dumps all of its energy” how is a wound channel being created below the dermis?

For pistols with a barrel length above 3.5”:
I would recommend sticking with 9mm. It’s cheap to plink/train with and 9mm guns have the strongest aftermarket currently. For defensive purposes I would advise sticking with Federal HST and Speer Gold Dot. You can get 50rds of either for $20 if you look around. They’re consistent, proven, and on the FBI’s approved list.

For pistols below 3.5”:
My money gets put on .40S&W. From testing I have seen and the studies I’ve read .40S&W, more specifically the 165gr loadings stick closer to advertised velocities than 9mm loads. For some referencing checkout Ballistics By The Inch. This isn’t to say that 9mm won’t do an adequate job out of barrel lengths shorter than 3.5″ out of a pistol.

For Pistols 4″ and above:
When not considering any of the factors besides wounding capabilities, the choice is really yours. I prefer 9mm due to the improved capacity, cheapness of training ammunition, and ease of use.

For Micro Pistols like the Ruger LCP II and Sig Sauer P938, I would recommend going with .380ACP. If your primary carry gun is this size, follow-up shots are going to be important; especially with limited capacity. .380ACP being the lower powered between it and 9mm  it’s going to have less recoil, so follow-up shots should be easier.
As an exception, if you know you’re going to dedicate the time to learning how to shoot, how to change magazines, etc. I would change my previous recommendation from .380ACP to 9mm. 

For .22lr or .22mag, I would urge you to look at revolvers. You get a lower chance of a light primer strike/failure to fire and you don’t have to worry about rim lock.

For Revolvers 3″ and above:

Unless your hands are weak, I would recommend going with .357Magnum. If your hands are weak, using a .38Spl or 9mm loading won’t hurt, but not in anything longer than 3″ (where .357Magnum really starts to pull away performance wise).

For Revolvers 3″ and below:

For snub nosed revolvers, you’ve probably already guessed that I’m going to recommend going with .38Spl. Faster follow-up shots, substantially easier recoil mitigation, paired with meeting, or surpassing FBI standards through denim is great. Especially considering it’s doing it out of a gun that weighs the same as a Ruger LCP II.

Stay away from:
Single Action Only Revolvers like the NAA Mini-Revolver for defensive purposes
Gimmicky ammunition like G2 R.I.P

When it doubt, message me on Facebook.

Thank you for reading this part of the First Time Buyer’s Guide to Handguns! Be sure to check out the other parts linked below!

Part 0: Stuff You Should Know Before Buying

Part 1: Handgun Actions Explained

Part 2: Handgun Frames Explained

Part 3: Handgun Calibers Explained (Currently On)

Part 4: Handgun Holsters Explained 

Part 5: Stuff You Should Know After Buying