Best Ammo for the Sig P320 and M17/M18

The pistol that won the Army contract

In January 2017, a customized Sig Sauer P320 won the U.S. Army's Modular Handgun System competition. The full-size version became the M17, the carry-size version the M18, and the first pistols reached the 101st Airborne Division that November. The program planned for up to 421,000 pistols across the services.

Something else changed at the same time. For the first time in a long while, a U.S. Army sidearm program cleared the way for expanding ammunition. The contract covered XM1152 full metal jacket ball and an XM1153 "Special Purpose" round, and a Pentagon legal review allowed the Army to consider hollow points. The Army's reasoning, as summarized in the program's reference entry, was that expanding bullets put most of their energy into the target and usually don't pass through, which limits collateral effects.

That's the same logic most civilian and police carriers use. So here's how to feed a P320, M17 or M18 for each job you'll ask of it.

Know your barrel first

The P320 is modular. Its fire control unit is removable and can move between grip modules and slide sizes, so "a P320" could be a full-size, a carry or a compact. Barrel length changes how fast any load leaves the muzzle, so check yours.

Barrel lengths for the M17 and M18 come from the pistol's reference entry. For other configurations, use Sig Sauer's spec sheet for your exact model.

Best for duty and carry

These are law-enforcement-grade hollow points that are widely used in service pistols of the M17 and M18's size. Velocity figures are the maker data shown on Ammunition Depot's product listings.

Why these three

All three are designed for service-size guns, which is exactly what the M17 and M18 are. They also represent the three main design philosophies: HST's non-bonded jacket, Gold Dot's bonded jacket, and Critical Duty's FlexLock with its InterLock band and polymer tip. If you want to dig deeper, see our Gold Dot vs Critical Duty comparison.

Sig's own option

Sig Sauer makes its own Elite Performance line, including the V-Crown jacketed hollow point. Ammunition Depot lists Sig Elite Performance 9mm under its 9mm section, but we couldn't confirm a specific V-Crown product page, so browse that section. Pairing a Sig gun with Sig ammo is a sensible choice, not a requirement.

Best for the range

The ideal practice round matches your carry load's weight, so the recoil and point of impact feel familiar. That's why 124-grain FMJ is the classic pairing for 124-grain +P carry ammo, and 147-grain FMJ goes with 147-grain HST.

Other practice options at Ammunition Depot include Blazer Brass 115 gr FMJ, a common, lighter range load, and Speer Lawman 115 gr TMJ, whose totally enclosed jacket covers the base. For a deeper look at range ammo choices, see our 9mm range ammo guide.

What about mil-spec M1152 and M1153?

It's natural to want "what the Army uses." The honest answer is that you don't need it. The XM1152 is a full metal jacket ball round, functionally similar to good commercial FMJ for practice. The XM1153 Special Purpose round fills the role commercial duty hollow points already fill. The duty loads above have long histories in police service pistols, and they're far easier to find in civilian packaging.

If you do come across commercial versions of the military loads, treat them like any other ammunition: verify the weight and pressure, test them in your pistol, and don't assume a military label means a better fit for your gun.

Magazines are part of reliability

A P320 that runs perfectly with one magazine and stutters with another usually has a magazine problem, not an ammo problem. When testing a carry load, use every magazine you plan to carry. The M17 and M18 typically use 17-round magazines, with 21-round extended magazines also offered. Ammunition Depot carries P320 magazines if you need spares. Magazine capacity limits vary by state.

A note on the P320's history

The P320 has had a complicated public record. In August 2017, Sig announced a voluntary upgrade program after drop-safety concerns with early production pistols. Since 2025, the pistol has been the subject of litigation and of differing decisions by agencies and organizations, with Sig maintaining that the pistol cannot fire without a trigger pull. If you own one, check Sig Sauer's website for any notices that apply to your serial number and follow the manufacturer's guidance.

Picks by owner type

The new owner with one P320

Start with one carry load and one practice load in the same weight. Federal HST 147 gr with a 147-grain FMJ is a simple, standard-pressure pair. If your model is +P rated and you prefer a faster load, Gold Dot 124 gr +P with Blazer Brass 124 gr is the classic pairing. Spend most of your budget on practice, not on stockpiling premium hollow points.

The owner who swaps slides and grips

The P320's modularity means one fire control unit could live in a full-size frame this month and a carry frame next month. Each configuration changes barrel length, so re-check point of impact and reliability every time you swap, and consider whether the load you chose for the 4.7-inch barrel still makes sense in a shorter one.

The suppressor owner

If your P320 has a threaded barrel and you shoot suppressed where it's legal, heavier 147-grain loads that start slower are the usual choice. Ammunition Depot's listing for HST 147 gr includes subsonic and suppressed use, and our subsonic vs supersonic guide explains why.

The home-defense owner

A full-size P320 or M17 with a weapon light is a common nightstand setup. The same duty hollow points work well, and the over-penetration concerns are the same as for any 9mm. Read our home defense ammo guide, and keep the pistol in a quick-access safe when it isn't in your control.

How to choose in three steps

1. Pick your carry weight. 124 gr +P if your gun is rated for it and you like a faster load; 147 gr if you prefer standard pressure and a softer push.
2. Buy enough to test. Run your carry load through every magazine until you're confident it feeds and ejects, and confirm it hits where your sights point.
3. Practice with the same weight. Use FMJ in the matching weight for most of your training.

The short list

Editorial note: This is an independent editorial overview built from manufacturer specifications, retailer listings and published sources. We have not performed hands-on testing of the products discussed, and nothing here is a performance guarantee. Verify specifications, compatibility and the law where you live.

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.