.45 GAP Vs .45 ACP Cartridges: Everything You Need to Know

45 gap vs 45 acp cartridge comparison

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When talking about .45 caliber, most people immediately think of the .45 GAP cartridge because it’s the most popular semi-automatic pistol bullet. However, that was not always the case as the ACP cartridge was the first one available. Things changed in 2003 when the .45 GAP was introduced as an alternative and an upgrade. In this article, we’re looking at the .45 GAP vs .45 ACP cartridges to point out the differences, pros, and cons for each type, and help you decide on the best fit for you.

.45 GAP vs .45 ACP: Cartridges Overview

Before jumping into comparing the two types of .45 cartridges, it’s important to take a close look at the characteristics of each type of bullet and understand what everything is all about. So, for all our readers wondering “What does GAP stand for in guns?”, the answer is Glock Automatic Pistol.  As a general rule, you need to know that the ACP is the first generation of .45 bullets and it was replaced by the GAP after over 70 years of service in the US Army and numerous other law enforcement agencies across the globe. On the other hand, the .45 GAP had a much shorter life before being replaced with the 9mm cartridges. But even so, it’s still in use in at least 4 states in the US.

What is .45 ACP

Designer John Browning
Designed 1904
Manufacturer Colt
Produced 1905 – present
Case Type Straight, rimless
Bullet diameter .452 inch
Case Length .898 inch
Overall Length 1.275 inch
Primer Type Large Pistol
Max Pressure 21000 PSI

While creating these .45 GAP and .45 ACP reviews, we learned that the .45 ACP (Automatic Colt Pistol) has been around for a very long time. Namely 1904 when John Moses Browning designed it for the US military. The older .38 or .30 ammunition was proving to be inefficient in battle and that became evident after the Moro Rebellion. In the need for a larger caliber cartridge, the .45 was considered to be ideal as it wasn’t too heavy compared to previous ammunition and it provided a larger cavity wound, as well as improved stopping power. The .45 ACP made the transition towards modern firearms thanks to its improved design qualities – full metal jacket, increased stopping power, shorter compared to the .45 Colt used by the Cavalry before.

Even though its activity starts with 1904, when talking about .45 ACP vs GAP, don’t think of the ACP as a cartridge that’s history. This bullet was used by the US Army until 1985 before switching to the 9mm Berretta, however, it’s still being used by State Police in some states like Pennsylvania. When it comes to civilians, there are many handguns that are ideal for .45 ACP bullets such as the Glock 39, Smith & Wesson M&P45 Compact, or even Sig Sauer P250.

Pros and Cons

Pros Cons
  • Improved stopping power than .38 and .30 bullets
  • Tested in combat
  • Over 70 years in the service
  • The large pistol primer
  • Slightly heavier than .45 GAP

What is .45 GAP

Designer Ernest Durham
Designed 2002
Manufacturer CCI/Speer
Produced 2003-present
Case Type Rimless and straight
Bullet diameter .451 inch
Case Length .755 inch
Overall Length 1.070 inch
Primer Type Small pistol
Max Pressure 23000 PSI

Continuing our .45 GAP vs .45 ACP overview, let’s take a closer look at the .45 GAP, the bullet that took all the best parts of the ACP and took it to the next level. It was developed in 2003 when Glock joined forces with CCI/Speer to develop a new cartridge for the .45 caliber firearms after the market was dominated by .45 ACP and its variations. When talking about the main improvements of the .45 GAP vs ACP, we need to start with the shorter size and the smaller pistol primer. It was designed to operate at higher standard pressures and also comes with a smaller cartridge volume which makes it faster when fired from a .45 pistol.

The .45 GAP was immediately adopted by modern law enforcement across the globe. Despite being eventually replaced by the 9 mm bullets all across the US, the law enforcement agencies in four states decided to switch back to weapons using the .45 GAP – New York, Georgia, Florida, and South Carolina.

.45 GAP vs .45 ACP: Main Differences Explained

As you can easily notice from the paragraphs above, there’s more than one difference between the .45 ACP and .45 auto bullets. Besides the .45 ACP being the designed cartridge for 1911 magazines, there are some fine details that set the two bullet types apart. So, after checking the .45 GAP and .45 ACP reviews, it’s time to summarize the main things that set these two apart.


While there’s not a big difference in the design when talking about .45 GAP vs .45 ACP cartridges, the fact that the GAP is slightly shorter can have a considerable impact. For example, in real-life situations, the larger guns that use .45 ACP can prove more difficult to handle. However, the lower functioning pressure of the ACP gives it less recoil than the GAP, sometimes improving accuracy.


Continuing the idea in the previous section, the .45 GAP and the pistols that operate it were considered more accurate by the law enforcement agencies that tried it. This comes from the shorter overall length which also helps smaller-stature shooters hold the grip more efficiently.


You probably already know this one after reading the .45 GAP reviews and history we presented above. Even though the pressure of .45 GAP cartridges increased to 23000 PSI, the ACP bullets remain more powerful since they’re longer. So, the fact they fire at around 21000 PSI doesn’t make them less powerful, it’s all about the length.


Despite being presented as the “new-and-improved” .45 caliber bullet, the GAP had a rather short life and it didn’t really manage to make a mark in the firearm industry. It was replaced by the 9mm Beretta rather quickly compared to the longevity of the .45 ACP and its variants.


While the debate between .45 GAP vs .45 ACP cartridges won’t end too soon, you now have all the data needed to choose the best type of bullets for our .45 caliber pistol. Just keep in mind that some users reported finding .45 GAP bullets a bit difficult compared to their ACP counterparts. However, they are also a lot more precise and powerful. So choose the model according to your needs, and feel free to share with us your experience and recommendations regarding .45 GAP vs .45 Auto.