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ARMAG

Search matches names, aliases and the text of every page. An arm found by its service designation is found by its alias, not its title.

20 gauge

SAAMI standard

Also known as 20/70, 20 bore — the same cartridge under different names, all of which find this page.

Dimensions and pressure

Generated from the schema, like every specification table on this site, so a figure recorded on this entry cannot be missing from the table.

Identity
Designed by
not recorded
Introduced
not recorded
Production
not recorded
Standards body
SAAMI
Case type
Shotshell
Case shape
not recorded
Dimensions
Bullet diameter
not recorded
Bore diameter
15.62 mm0.6150 insource

Bore diameter of the SAAMI 20-gauge standard smoothbore test barrel, 0.615 in.

Case length
69.8 mm2.748 insource

Cartridge maximum for the 20/70 shell, dimension l.

Overall length
not recorded

No free source publishes a loaded length for a 20-gauge shell, and the figure varies with the crimp and the payload.

Rim diameter
19.4 mm0.7638 insource

Cartridge maximum, dimension g.

Neck diameter
not recorded
Base diameter
17.7 mm0.6969 insource

Cartridge maximum, dimension d.

Pressure
Maximum pressure
83 MPa12,038 psisource

Pmax for the 20/70 shell, 830 bar.

Pressure standard
C.I.P.

SAAMI and C.I.P. measure pressure differently and their figures are not interchangeable, which is why the body is always named beside the figure.

Loads

No load data recorded yet. Without a sourced bullet mass and velocity there is nothing honest to compute, so the ballistic figures on pages that chamber this cartridge stay blank rather than being estimated into existence.

Chambered in

Computed from every entry that lists this cartridge. Nothing here is hand-maintained.

Detail

The 20 is the smaller of the two shotgun bores in general use, and the pressure ceiling C.I.P. sets for it is higher than the 12’s: a narrower bore means a smaller area for the gas to work against, so more pressure is needed for the same result. Shooters who assume the smaller gauge is the gentler one are half right, because what they feel is recoil, and recoil follows the mass being launched rather than the pressure behind it.

This is an identity-only entry. No load is recorded, so no page on this site quotes a muzzle velocity or an energy figure for a 20-gauge arm.

References

  1. C.I.P. TDCC datasheet, Cal. 20 · Tab. VII, dated 1984-06-14, revision 2020-11-10 · read 2026-08-27
  2. ANSI/SAAMI Z299.2, Shotshell Ammunition · Z299.2-2019, approved 2025-09-23 · read 2026-08-27

Last verified 2026-08-27 · review status: spot-checked