Glock 21 Magazine

Glock 21 Magazine: OEM and Extended .45 ACP Magazines for Gen 1 Through Gen 5

A Glock 21 magazine is a double-stack, polymer-bodied ammunition feeding device that holds 13 rounds of .45 ACP and inserts into the full-size Glock 21 grip. The Glock 21 is a large-frame Glock pistol chambered in .45 ACP (Automatic Colt Pistol) with a 4.61-inch (117 mm) barrel. The OEM Glock 21 magazine uses a hardened steel insert encased in polymer with steel-lined feed lips and a coated compression spring. TactaBlue stocks Glock 21 magazines from Glock OEM, KRISS, RWB, KCI, SGM Tactical, and ProMag in standard and extended capacities.

Glock 21 OEM Magazine Specifications

The Glock 21 OEM magazine specifications are:

• Caliber: .45 ACP (11.43x23mm)
• Standard capacity: 13 rounds
• Body material: Polymer with hardened steel insert
• Feed lip material: Steel-lined
• Spring: Coated steel compression spring
• Follower: Polymer (orange on Gen 5)
• Floor plate: Polymer with ambidextrous release notch

The Glock 21 Gen 5 10-round magazine is a state-compliant version for jurisdictions that restrict magazine capacity to 10 rounds. The 10-round magazine uses the same magazine body dimensions as the 13-round version with a limiter that prevents loading beyond 10 rounds.

Glock 21 Extended Magazine Options

KRISS Vector MagEx2 Glock G21 .45 ACP 30-Round Magazine

The KRISS Vector MagEx2 for the Glock 21 is a 30-round .45 ACP extended magazine that uses a KRISS magazine extension body attached to a Glock OEM magazine. The MagEx2 more than doubles the standard 13-round capacity. The MagEx2 is compatible with the Glock 21, Glock 30, Glock 30S, and Glock 41.

RWB Glock G21 .45 ACP 26-Round Magazine

The RWB (Red, White, and Blue) Glock G21 26-round magazine is an aftermarket polymer magazine that doubles the standard 13-round capacity. RWB also manufactures a 26-round .45 ACP magazine in tan (FDE) polymer. The RWB 40-round .45 ACP drum magazine provides the highest capacity option for the Glock 21 platform.

KCI Glock .45 ACP 26-Round Magazine

The KCI Glock .45 ACP 26-round Gen 2 magazine fits the Glock 21, Glock 30, Glock 30S, and Glock 41. KCI magazines use a polymer body with steel-lined feed lips and an anti-tilt follower.

SGM Tactical .45 ACP 13-Round Magazine

The SGM Tactical .45 ACP 13-round magazine for the Glock 21 is an aftermarket replacement that matches OEM capacity at a lower price point. SGM Tactical magazines use a polymer body with steel feed lips.

ProMag Polymer Magazine Glock 21 .45 ACP 13-Round

The ProMag Glock 21 .45 ACP 13-round polymer magazine is an aftermarket standard-capacity replacement with a heat-treated chrome silicon wire spring and injection-molded polymer follower.

Glock 21 Magazine Compatibility

The Glock 21 magazine is compatible with 4 Glock models in .45 ACP: the Glock 21 (full-size), Glock 30 (subcompact, magazine extends below grip), Glock 30S (subcompact slim slide), and Glock 41 (long-slide competition). The Glock 30 10-round .45 ACP magazine fits the Glock 21 but does not fill the full-size grip. Large-frame .45 ACP Glock magazines are not compatible with standard-frame (G17/G19) or compact-frame (G26) models.

Glock 21 Magazine Maintenance

Glock 21 .45 ACP magazines require spring replacement every 5,000 to 8,000 rounds to maintain consistent feed pressure. The .45 ACP cartridge (operating pressure: 21,000 psi SAAMI) is physically larger than 9mm (case diameter: 12.09mm vs. 9.93mm), which means the follower and spring travel a greater distance per cycle. Inspect feed lips for spreading or cracking every 2,000 rounds. Clean the magazine body and spring after exposure to dirt, sand, or moisture. Check the witness holes on the magazine body for round-count verification during loading.

Glock 21 Magazine Accessories

Glock 21 magazine accessories include extended base plates that add +2 capacity, magazine loaders for the wide .45 ACP cartridge, and magazine pouches sized for the large-frame magazine body. A Glock magwell funnels the wide .45 ACP magazine into the G21 grip for faster reloads. Browse Glock 30 magazine extensions for the subcompact .45 ACP platform, Glock 17 magazines for the full-size 9mm platform, and all accessories for your Glock at TactaBlue. View the full Glock magazine catalog for all calibers and models.