A short history of 10mm in law enforcement
After the 1986 FBI Miami shootout, the Bureau looked for a more effective handgun cartridge and adopted 10mm in 1989. Full-power 10mm proved hard for many agents to control, so a reduced-velocity "10mm Lite" load followed. That shorter case led to the .40 S&W, which became the dominant American police cartridge for years. Later, improvements in 9mm bullet design and FBI testing moved the Bureau and most agencies back to 9mm. We cover that shift in our .40 S&W article.
Why 10mm is back in the conversation
Two things changed. First, modern 10mm pistols carry far more rounds than the single-stack guns of the 1980s. Second, interest grew among rural officers, wildlife officers and outdoors users who may face large animals as well as people. For those users, a 10mm that also carries a light and optic is appealing.
FN 510 Tactical
The 510 Tactical is FN's 10mm, based on the same family as the FN 509 Tactical. The catalog listing shows 22+1 capacity, a threaded barrel and an optics-ready slide. If you already know the 509, the controls carry over.
FN 510 Tactical
10mm · 22+1 · threaded, optics-ready
Sig P320-XTEN
The XTEN brings 10mm to the P320 platform with a 15+1 listing. For agencies already running P320s, it keeps the same manual of arms.
Sig P320-XTEN
10mm · 15+1
The honest trade-offs
| 9mm | 10mm | |
|---|---|---|
| Recoil | Mild | Stronger, load dependent |
| Training cost | Lowest | Higher |
| Capacity (same size gun) | Higher | Lower |
| Large-animal use | Marginal | Better suited |
| Holster and mag support | Enormous | Narrower |
Speed and accuracy under stress decide outcomes, and most shooters are faster and more accurate with 9mm. That is the main reason agencies stay with it.
Ammunition
10mm loads vary widely, from mild target loads to full-power hunting loads. For duty use, a bonded or controlled-expansion hollow point from a major maker is the norm. The catalog lists Federal's 200-grain HST 10mm.
Federal HST 10mm 200gr
Defensive hollow point
Who should consider 10mm for duty
- Rural and wildlife officers who may encounter large animals.
- Officers who already shoot 10mm well and have agency approval.
- Civilians in bear country who want one handgun for the woods and home. Our sister site WheelGuns covers revolver alternatives.
Bottom line
The FN 510 is a well-built modern 10mm, and it shows how far high-capacity 10mm has come. For most duty users, 9mm is still the better tool. For those with a real reason to need more, the 510 is a strong option.
Frequently asked questions
Did the FBI use 10mm?
Yes. The FBI adopted 10mm in 1989 after the 1986 Miami shootout, then moved to a reduced load and later to .40 S&W and 9mm.
How many rounds does the FN 510 Tactical hold?
The catalog listing shows 22+1 with the included magazine. Check your state's magazine limits.
Is 10mm good for duty use?
It is powerful and capable, but harder for many shooters to control than 9mm and more expensive to train with. Most agencies use 9mm.
Is 10mm good for bear defense?
Many outdoors users choose 10mm for large animals because it offers more penetration than 9mm with high capacity.
Keep reading
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