Which Cartridges SAAMI Says a Chamber May Generally Shoot

By Cole Harlan, Editor·Checked Nov 5, 2026·How we verify·Editorial standards·Corrections

Read this first: what SAAMI says

“Firearms should only be used with the ammunition designated by the firearm manufacturer for use in that firearm.”

“Remember – just because a round of ammunition can fit into a firearm’s chamber, barrel, or action – this does not necessarily mean that it is safe to use that ammunition in that firearm.”

SAAMI says the combinations in the table below are “limited to only the following,” and that even for these the user “should always refer to the firearm manufacturer prior to use.” Check the head stamp of the ammunition against the marking on the firearm. Nothing on this page is a recommendation to shoot anything.

Which cartridges a chamber may generally shoot

20 chambers and 35 alternate cartridges, copied from SAAMI’s PDF. Each row is one chamber and the alternates SAAMI lists for it. Other pairs are not on SAAMI’s list, including look-alikes.

Shotshells: length and gauge

• Shorter shell, same gauge, longer chamber: acceptable. SAAMI gives the example of 12-gauge 1¾″ or 2¾″ shells in a 12-gauge 3″ or 3½″ chamber. It adds that the user should still refer to the firearm manufacturer if the gun is not marked for the shorter shell.
• The reverse is not true. SAAMI’s words: “The reverse is NOT TRUE as the longer shell will produce higher-than-expected pressure either by design or from the mouth of the shell opening into the forcing cone of the shorter chamber and creating a constriction.”
• Different gauges are never interchangeable. SAAMI: “Different gauges are NEVER interchangeable, and some mix-ups are known to have the potential to cause catastrophic results.” It names the “12/20 burst” (a 20-gauge shell lodging in a 12-gauge forcing cone), and says a 16-gauge shell in a 12-gauge chamber, a 20-gauge shell in a 16-gauge chamber, or a 28-gauge shell in a 20-gauge chamber can cause the same outcome.

Shotshell pressures for 12 gauge, 20 gauge and .410 bore are on our SAAMI MAP chart. Guides: 12 gauge, 20 gauge and .410 bore.

Commercial vs military ammunition

SAAMI says ammunition made to military standards “can have higher pressure levels than their commercial counterparts,” and that surplus military firearms may have headspace within a military standard but excessive for a SAAMI commercial cartridge. Its examples are 223 Remington / 5.56 x 45mm NATO and 7.62 x 51mm NATO / 308 Winchester. Its instruction: “only use ammunition manufactured to military standards in firearms that are marked and chambered explicitly to accept that specific military cartridge.” These are not listed as safe pairs. For 223 Remington and 5.56 specifically, the PDF sends readers to SAAMI’s FAQs.

SAAMI’s June 22, 2026 public introduction of 5.56 Commercial repeats the warning: “Existing guidance that ONLY 223 Remington ammunition is to be used in a firearm chambered and roll marked as only “223 Remington” remains unchanged. The use of any 5.56 ammunition, including all military variants as well as ammunition produced to this standard in a 223 Remington chamber creates increased pressure and is considered an unsafe combination.” See 5.56 vs .223, the 5.56 and .223 ammo guide and the 5.56 Commercial row on the SAAMI MAP chart.

Method

• Source. SAAMI’s own PDF, dated 10/8/2021, read on Nov 5, 2026. Each row is one chamber and alternate pair from its table; nothing is added, merged or inferred.
• Names. Full and abbreviated names are SAAMI’s. SAAMI lists equivalent and historical cartridge names separately on its advisories page; we do not repeat them here.
• Licence. Our compilation is CC BY 4.0. The chart belongs to SAAMI.

How we check these figures: How we track, editorial standards and corrections.

Download the data

saami-interchangeability.csv has one row per chamber and alternate pair (35 rows) with SAAMI’s full and abbreviated names, the source PDF, its date and our checked date. Free to reuse under CC BY 4.0.

Related

• SAAMI MAP pressure chart
• 5.56 vs .223
• 5.56 and .223 ammo guide
• 300 Blackout ammo guide
• 12 gauge ammo guide
• .38 Special ammo guide
• .357 Magnum ammo guide
• 357 SIG ammo guide
• .22 LR ammo guide
• All GunReleases data

Frequently asked questions

Sources

1. SAAMI: Generally Accepted Firearms and Ammunition Interchangeability (10/8/2021)
2. SAAMI: FAQs
3. SAAMI: SAAMI public introduction: 5.56 Commercial (5.56 COMM), issued June 22, 2026

Last checked 2026-11-05.