There is an ongoing debate about whether 9mm or .45 ACP is the better caliber. Some are quite religious about their preferred caliber. Today we wanted to give you some information about both and then let you decide on which one suits you best. 

The bullet size is important because a larger bullet will cover more surface area upon penetration, retain better accuracy with a suppressor, and greater capacity for holding gunpowder. A smaller bullet has greater muzzle velocity, deeper penetration after impact, and substantially reduced noise with a suppressor. The 9mm is a smaller round with a diameter of 9 millimeters and the .45 ACP is 11.5 millimeters.  You might think that two millimeters is not that much of a difference, but it matters.

The recoil of the 9mm is much less compared to the .45 ACP. It is quick and easier to adapt to, while the .45 ACP has an aggressive recoil that requires particular training to get used to. Likewise, the 9mm has a higher muzzle velocity which means it has a higher terminal performance than the .45 ACP. However, the size of the .45 ACP makes for larger surface area for mushrooming on impact, given you are shooting hollow points.

The last few points we are going to discuss are the size and capacity. The 9mm is smaller and can have a higher capacity of rounds. The .45 ACP is larger and has a lower capacity since the bullets are larger. This means that it is easier to conceal most 9mm pistols compared to similar .45 ACP pistols. At the end of the day it is a personal decision and preference.

Let us know which caliber you prefer and why that is!


Add Comment


Rich Hughes

Date 10/4/2021

Hi , I like your views on the differences between 9mm and 45acp . I would add in the difference that velocity has on the two calibers. The 9mm travels around 1340 fps and the small size produces paper punch holes with little collateral damage while the larger diameter and increased weight 45acp travels at a very slow 850 fps (any respectable spring action .177 pellet gun goes almost twice that fast with alloy ammo) and while punching a large hole it also creates hydro shock and bleed out. Also is the effect of the impact , which moves the target as opposed to the 9mm which zips right through a target. I am talking about using fmj standard ammo . Could you folks work on a spring /bolt combo along with lighter load 9mm round that would bring the fps down to 850 ? It might be a new close combat round that has real knock down power . Thank you for taking time to read my e-mail , Rich

Tim Daley

Date 1/28/2022

I am looking for a complete AR upper in 45 cal between 8.5" and 10"

Sam h

Date 2/14/2022

I need a 45 upper when will you have more

Paul Hall

Date 7/18/2022

I have a question on the AR15 45acp upper. I see it's offered with S&W magazine, Would there be any issue using a Stern adapter with Glock mags? I would assume not but I have to ask. I'd rather know before I build it and have surprise. Thanks and help appreciated guys. Paul

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