FN 510 Tactical vs FN 545 Tactical: 10mm or .45 ACP?

Both are modern, high-capacity, optics-ready answers to the question of what comes after 9mm. They are very different answers.

Why this comparison exists

For decades a duty pistol conversation meant choosing a caliber, and for most of the last decade the answer in much of American law enforcement has been 9mm. But two things keep a big-bore conversation alive: some officers work in environments that put large animals in the picture, and some simply prefer a heavier bullet. FN's Tactical line gives both camps a modern, high-capacity pistol, in two different cartridges.

We discussed the 10mm model on its own in FN 510 Tactical: is 10mm a duty round again?. This piece puts it next to its .45 ACP sibling. Both are related to the pistol we reviewed in the FN 509 Tactical review, which is worth reading first if the family is unfamiliar.

The numbers that are on the listings

We have not verified weights, dimensions or barrel lengths from the manufacturer, so those are left out. Check FN's published specifications before you decide.

Capacity is the first difference. Both pistols hold a large number of rounds for their calibers, and the 10mm holds more in its listed configuration. Larger magazines also mean larger grips, so hand fit matters. Pick up the actual gun if you can.

The cartridges, in plain terms

10mm Auto

10mm is a full-power cartridge with a long history, including an adoption by the FBI in the late 1980s and a retreat from it when many agents found it hard to control, a story our FN 510 article summarizes. Loads vary widely from mild to heavy, so the experience of shooting 10mm depends heavily on the ammunition. A modern high-capacity pistol makes the cartridge more practical than the single-stack guns of its early years.

.45 ACP

.45 ACP is a larger-diameter, slower cartridge with a very long service history, in the military and in law enforcement. Its recoil impulse is often described as more of a push than a snap, and plenty of shooters find it easy to manage in a pistol of sufficient size. Ammunition is widely available, in practice and defensive varieties. Our sister sites explore the trade-offs in their 10mm versus .45 ACP comparison.

Choosing by problem, not by cartridge

A useful way to decide is to start with what you need the pistol to do.

You work in rural or wildlife-heavy country. 10mm is the commonly cited choice for that environment, because of the heavier and faster bullet options. DefensiveHandgun covers it from the woods-carry angle in its 10mm carry pistols article. Make sure any load is one your agency approves.

You want a familiar cartridge with a long record. .45 ACP has decades of experience behind it, and many officers already know it. It also means more practice and defensive options, and a recoil feel that many consider manageable.

You want maximum capacity. The 10mm listing is higher at 22+1 versus 18+1.

You want the broadest ammunition support. Neither beats 9mm. Both are less common on shelves, and training volume is a real cost for any big-bore pistol.

Costs that do not show up on the listing

Big-bore ammunition is more expensive to train with than 9mm, and training volume is what keeps skills sharp. A pistol you cannot afford to shoot enough is a poorer duty pistol than one you can. That does not make big-bore wrong, but plan the training budget before you plan the pistol. Our training ammo guide explains how to match practice to a duty load.

Holsters are the other hidden cost. Both pistols are large and carry an optic, and the owner needs a holster molded for that setup, with a light if you add one. See duty holster retention levels for how to think about it. Confirm exact model compatibility with the holster maker.

Agency reality

Agencies typically authorize a narrow list of calibers and models, and a big-bore pistol may or may not be on yours. If you carry for work, ask. If you carry for yourself, make your choice with the same attention to training that an agency would require.

Pick this if / pick that if

Magazines, grips and reload math

Capacity numbers do not tell you the whole story, because a big magazine implies a big grip. A 22-round 10mm magazine and an 18-round .45 ACP magazine both require a substantial grip frame, and that frame determines whether your hand reaches the trigger comfortably. If you have smaller hands, this is a bigger factor than caliber.

Reloads matter too. Larger magazines are heavier and longer, and pouches must be sized for them. If you plan to carry spares on a duty belt, check that your pouches hold the specific magazine securely and that the belt can carry the weight comfortably, a point our duty belt setup guide explains. Mark and number magazines, and test each one for function before trusting it.

The sensible default

If you are not sure, you probably want a 9mm. A Glock 17 Gen5 or an FN 509 Tactical gives you more training per dollar, the most holster options, and the easiest agency path. The big-bore Tactical pistols are for people who know why they want them.

Confirm every specification and approval with FN, your agency and the retailer before buying.

Editorial note: This is an independent editorial overview built from manufacturer specifications and publicly available information. We have not performed hands-on testing of the products discussed, and nothing here is a performance guarantee. Verify specifications, compatibility and legality for your own situation.

Affiliate disclosure: Some links on this page are affiliate links to Ammunition Depot. We may earn a commission if you buy through them, at no extra cost to you. Our editorial choices are not influenced by commissions. Check current price, stock and specifications directly with the retailer.