45 GAP, the Glock 37, & the Caliber That Should Have Been

Gen 3 Glock 37

This week, we are going to take a look at an odd one, and not just for historical reasons. I was able to procure a Glock 37 and 1000 rounds of ammo to feed it recently for $800. That is a used gun off the secondary market, but it was available and not badly priced. Considering how crazy the gun market has been, you could do a lot worse. Why could it be had at that price? Because a Glock 37 is chambered in 45 GAP.

Slide width next to a G19

What is 45 GAP, some of our younger audience may be asking? 45 GAP was a cartridge developed at the behest of Glock around 2002, to mimic the ballistics of 45 ACP in a small frame pistol. One could call it 45 Short and not be wrong. The principle was to make a 45 caliber cartridge that would be equal or close to John Moses Browning’s (peace be upon him) 45 ACP, the American standard since 1904. Which itself was built to mimic or exceed the 45 Long Colt, in a much shorter package that would feed from an automatic pistol. So basically it was attempting to evolve the American love affair with 45 caliber into a slightly smaller gun, which briefed really well. But didn’t ever really catch on.

9mm and 45 GAP share the same size mag body

If you look at the Glock 37, you could easily mistake it for a Glock 17. This is fortunate because there are only so many reviews we can write on a Glock. So imagine gripping a Glock 17, but when you look at the slide, it is more like a 45 ACP or 10mm. That isn’t quite true, as the G37 ( 45 GAP) is actually 4/100ths of an inch smaller than the G21 (45 ACP). But close enough. It is effectively like having a G17 grip with a slightly fat slide that throws 45 caliber projectiles. Which sounds pretty cool. So what happened?

The unmistakable sight of a 45 caliber bore

That lends itself to a lot of conjecture. Personally, and I was around when the 45 GAP hit the market, it seems like Americans just didn’t want to have a 45 option that wasn’t a 1911. In the early 2000s, it was like you have a choice. You shot 9mm or 40S&W out of a plastic gun, or you shot 45 ACP out of a 1911. Striker fired pistols had nowhere near the market dominance they do now, and it was rare to see a Glock in the wild where I lived. They were making great strides in the LE market, but in many ways, the civilian shooter still preferred a 1911. Or a 9mm. And very rarely both.

45 GAP left, 45 ACP right

The other thing working against the 45 GAP was timing. It was developed and got its SAMMI Spec in 2002 and hit the market in Glock pistols in 2003. Now it had a good chance of taking over in a world of 10 round magazines. Which is what we were all stuck with around that time. Kids today will never know the pain of paying $100 for a SINGLE drop free high-capacity Glock 17 round magazine. (They might soon actually, given the state of the economy. But not the point.) Back during the “assault weapons ban”, that was common. If you could find one. Every magazine made before 1994 was grandfathered and therefore legal. And once again, Glock wasn’t all that popular in 1994. Ergo, there were not container loads of hi-capacity mags floating around, including 15 aftermarket suppliers.

45 ACP crammed into a 45 GAP magazine

I don’t think any of us expected the AWB ban to actually sunset in 2004, but it did. Overnight, you could purchase grown-up magazines again as long as you didn’t live in NY, Taxachussets, or Commie-fornia. The 45 GAP had been developed in the 10 round magazine era, and probably never engineered to get more. Now let’s say you are Glock, and the ban has just expired. You have machines that can turn out magazines all day and night for a hungry public. You have the prints in front of you for hi-capacity 9mm and 40S&W magazines. Do you hit the go button on things you already know how to make, or do you devote R&D time to maybe getting the 45 GAP up to 13? Me too. And as far as I know, to this day, no one makes a 45 GAP magazine that holds more than 10.

9mm, 40S&W, 45 GAP, and 45 ACP

The 45 GAP did see some initial success, most famously as the weapon of choice for the NYPD. But it seemed like it was never enough. With 9mm, 40S&W, 45 ACP, and 357 SIG battling it out, there really wasn’t room for a 5th. As time went on, and 45 GAP didn’t get more traction, ammunition slowly got more and more expensive. Which made it even more unpopular. As far as I know, only one other gun was ever chambered in 45 GAP, outside of Glock. Springfield Armory had a single model of original XD in 45 GAP, which is very hard to find.

This isn’t even my first rodeo with 45 GAP, though it is my first time shooting it. A few years back, I borrowed a G37 from Glock. But when I went to source ammo, Federal had some bad news. They made 45 GAP exactly once a year, to fill the needs of the NYPD, who still issued G37’s. I would have to wait a full year, so the G37 went back to Glock unfired.

Top view of the same lineup.

So why are we talking about it now? Because the relative scarcity of guns and durability of ammunition have made it an absolute outlier. Even when ammo was absolutely nuts, 45 GAP seemed inflation-proof. When 9mm was approaching $1 per round, you could find 45 GAP at 40 cents all day long on AmmoSeek. There were a lot of cases of ammo bought by distributors that have been gathering dust on the shelves for years. This means it is a very viable option if you are way late to the party of getting armed. Or arguably, want to train with a Glock pistol but not pay 9mm prices.

How does it perform? Well, I am very happy with mine. It feels pretty much like 45 ACP recoil but has a 9mm handle to hold onto. Modern powders have caught the 45 GAP up to true 45 ACP speed and beyond, with a full 230-grain bullet. The G37 actually has mag bodies the same size as a G17, that isn’t an exaggeration. Which is pretty cool. It’s a strange beast, but it has really grown on me. To the point I am thinking about adding a few thousand more freedom seeds to the basement, the G37 needs to eat. If you want one of your own, get it while the getting is good.

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About the author: Clay Martin is a former Marine and Green Beret, retiring out of 3rd Special Forces Group. He is a multi-decade and -service sniper, as well as 3-Gun competitor and Master ranked shooter in USPSA Production. In addition to writing about guns, he is the author of “Last Son of The War God,” a novel about shooting people that deserve it. You can also follow him on twitter, @offthe_res or his website, Off-The-Reservation.com

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  • MeSeaHunt August 26, 2022, 1:51 pm

    was issued one of these and when I held it for the first time all I could think was this is the GIRLS version of the MANS 30s….. so for me it was like a training pistol to my 30s which us lucky few feds were issued, and I still carry today! If I knew there was an abundance of never ending ammo for the GAP I would own one because it IS a great practice and backup piece…. they are available but like most things folks are asking WAY TOOOO much for them just because???

  • Grumpy 49 August 26, 2022, 12:51 pm

    Folks forgot that in Europe, the .45 ACP is illegal to own, (military cartridge), so they developed the .45 HP. At only a 1 mm shorter case than the .45 ACP, but the same OAL for the loaded cartridge, a 1911 could be re barreled to the .45 HP, and be then legal to own. Pressures were about .45 ACP +P level. The .45 GAP case is even shorter than the .45 HP, so IF you find a seller with .45 HP – 185 grain Hollow Point ammo, be aware that it is possible that it is NOT either .45 ACP or ,45 GAP compatible. Found that about the hard way. Good news was that I could salvage the bullets, powder, and primers to load .45 ACP rounds. Anyone need several hundred rounds of .45 HP brass??

  • Michael Koch August 26, 2022, 9:38 am

    I carry a Springfield in 45 GAP; bought it at Camp Perry ; It felt so good ind my hand, I could not put it down!

  • Chris Mace August 22, 2022, 9:13 pm

    If you ever find a solution to the 10rd mag issue. I’d be very interested to hear it. Ever since the AWB, I’ve had a strong dislike for 10rd mags on principle. I wonder if one of the floorplate type extensions might work for this caliber.

  • Scott August 22, 2022, 8:01 pm

    Glock 17 with 356 TSW conversion.

  • Todd August 22, 2022, 5:14 pm

    I recognize that inside any of several ballistics, manufacturers’ and consumers’ *bubbles*, things like the 10mm Kurz, .45 Kurz, .357 Sig, Action-Expresses, etc… and any of the myriad rifles of short and super short magnums make sense…. IN THOSE BUBBLES.

    However, out here in the real world where there is a long and storied history of *the next big thing* faltering for minuscule advantages and offered up still borne for the lack of platforms using it within the first year of introduction – A fella like me just can not help but chuckle when some starry-eyed reader prattles on with his “yeah, but….” and “but THIS one….” or “You HAVE to understand….”

    Then, as time passes, the calmer and broader appreciating owners either silently or vociferously retort with: “Told Ya So!”

  • Larry W Johnson August 22, 2022, 1:19 pm

    I bought one because it was a cop trade-in and it was a Glock and it was only $220. Now I am having trouble finding ammo for it, but I don’t shoot it much. Don’t really like Glocks, but I have them in 45 ACP, 40 S&W, 357 SIG, and 9mm so I keep a couple boxes just in case someone wants to shoot it or in case I want to sell it. It is in the back of the safe with the guns I don’t shoot. Never know, it might become a collectors item some day. Or it can always be a door stop.

  • Meeester August 22, 2022, 12:52 pm

    Since we have 40 SW we don’t need the other calibers in that picture.

    • Blue Dog (he/him) 🧢 August 22, 2022, 8:05 pm

      The .40 is the compromise that offers none of the advantages and all the shortcomings of all those cartridges in the pictures.

      • ej harbet August 25, 2022, 7:06 pm

        off to the shrink with me.
        I’m agreeing with Bluedog.
        it’ll pass 🤣.

  • Mike in a Truck August 22, 2022, 12:30 pm

    A stupid cartridge and even stupider pistol. Designed for affirmative action hires and split tails so as not to drop it and run away when touching it off. The 1911A1 and 45 ACP are still around and that Halloween abortion is gone. Good riddance.

  • Jay August 22, 2022, 11:50 am

    The Glock in .45GAP was also adopted and issued by the Pennsylvania State Police, they eventually moved to the Glock 21 in .45ACP and currently carry Sig’s..

  • Richard August 22, 2022, 11:21 am

    I carry a Glock 39 often.

  • Fal Phil August 22, 2022, 10:15 am

    “One could call it 45 Short and not be wrong. ”

    Can we call the 40 S&W a 10mm Short? That’s how a lot of folks think about it.

    • Justin S August 23, 2022, 2:37 am

      Foe years, the .40S&W was referred to as the “.40 Short & Weak.”

  • Tony August 22, 2022, 9:39 am

    My 45 Gaps are probably my most accurate Glocks. I shoot it much better then my G21 as the smaller frame fits my hand better. I used the G37 Gen 4 this past weekend at the Topton Pa. GSSF Match in the Heavy Metal Division. I finished 7th in the division. I would shoot it more often but I need to get some additional brass to reload.

  • Frank August 22, 2022, 9:25 am

    Ah… There you are, Clay! I’ve missed your writings. I lost track of you when “Off the Reservation” was discontinued. Just found the new site (Clay Martin Defense) and am looking forward to catching up. I too, can see the writing on the wall. While we still invest hope in the “ballot box”, we absolutely MUST invest our ever-shrinking dollars in the “AMMO box”!

  • Phil Wong August 22, 2022, 8:51 am

    According to Wikipedia, the New York [City] Police Department has never issued the Glock 37, but the New York *State Police* did issue the G37 from 2007-2018, at which point the State Troopers transitioned to the Gen 4 G21 in .45ACP…

    • Nick Carroll August 22, 2022, 10:19 am

      The PA State Police used it as well. I recall plenty of G37s showing up at my LGS when they dumped it. A lot of the officers had it transferred to themselves after the purge. Rarely ever see that round at the Range I work at though.

  • Carl childers August 22, 2022, 8:43 am

    45 GAP was and still is the most stupid caliber ever.

  • Slim August 22, 2022, 7:55 am

    Pretty descent info/column! I personally am a huge GLOCK fan as it’s my EDC pistol in either the G22(.40)or the G20T(10mm in tactical length slide/barrel)and of course also have the standards like the G17… blah blah. But the .45 caliber in either ACP or GAP I’m just not a fan of. Realistically with todays precision self defense rounds that reach speeds of 2,000 FPS plus the .45 anything really isn’t needed like it was years ago before speeds, projectile shapes, and projectile materials that can now be attained via a 9mm platform even with the shorter 3”ish barrels. So I myself would prefer the extra rounds than less with a bigger projectile. Speak to people who have been in actual shootings/self defense situations and especially the ones who ran empty would much rather be shooting more than bigger. Reality is in most cases ones ones shot they tend to retreat or worse for them instead of trying to stay and fight. There are many instances that prove my last sentence to be false as people on drugs like meth will a lot of the times keep coming even after full mags dumped into them so there’s of course people out there that can some how keep going and stay a threat. But I still feel in most cases people tend to opt out if they can which is good for both sides. Since I’m such a GLOCK fan and have built my own custom one offs from bare frames I also looked at .45 GAP barrels from Lone Wolf years back, but never pulled the trigger since I wanted my 10mm before a .45 GAP. But at the time they were trying to get rid of the barrels of all calibers they had(from china to move toward the alpha barrels i was told)and for the reasons negatively about the caliber I bet played a role in the lower price than others and in stock availability when most all others has been sold out. I to this day if I had the money or came across a real good deal on a barrel would of bought a .45 GAP barrel for my GLOCKS, until I read that they made only a ten round mag which reminds me of my aforementioned preference on rather having more rounds than bigger cones back to the front of my thoughts. 10 is just not enough these days since I’m sure anyone who’s been around the gun industry at all has heard someone repeat the old saying that’s goes something like “I have to much ammo,” said no one! Kind of a goofy saying, but in essence is true. But with all that blah blah I’ve never actually fired any gun, pistol or rifle in .45 GAP. But I have a few .45 ACP and stupidly fired just once without ears on and instant ringing of course which was my fault never to be repeated(worse than even my 10mm). But with that one shot I realized that caliber would be a terrible caliber for home defense since with the very first shot you’d be essentially deaf which isn’t great if a threat is in your home! I know I carry the G22 or G20T but recently have been building a G43X for my mom and a G48 for myself which are both 9mm’s and if I can get some reliable Shield Arms mags I’ll have a slim frame GLOCK that holds 15+1 in a much thinner package(especially regarding the .45 GAP’s slide width for conceal carry)as well as more weight and printing the larger .45 GAP has to have. The price you paid is fair these days and if I were you and money wasn’t a concern I’d take care of that pistol since I bet there’s not many left out in civilians hands that are in good shape. Sure it’ll probably never be a super rare or super expensive, but easily could be a nice conversation piece, rare caliber for a real shooter to try that hasn’t yet, and sure to stay or most likely slowly go up in value over the years due to it being more and more rare as days go by with functional things like the mag or mags you have that may be some expensive mags.

  • George August 22, 2022, 7:36 am

    I have a Glock mod. 39 45gap, I like the concealable factor and reliability of it.
    Enjoy shooting it often,

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