Glock G21 Gen5 MOS .45 ACP
Model: PA215S203MOS
Glock G21 Gen5 MOS .45 ACP
Model: PA215S203MOS
Full Specifications
About This Firearm
The Glock G21 Gen5 MOS carries 13+1 rounds of .45 ACP. That is 5 more rounds than every 1911 in this caliber and 3 more than the HK HK45 or Smith & Wesson M&P 45 M2.0. At 29.1 oz with a polymer frame, it weighs 12 oz less than the Sig 1911 Nitron, which changes the handling entirely. The MOS slide comes cut from the factory for direct-mount optics using adapter plates, and three magazines ship in the box.
The 5.5 lb striker-fired trigger is consistent pull-to-pull but lacks the clean break of the HK HK45's 4.5 lb DA/SA single-action pull. Owners report the Gen5 trigger is an improvement over the Gen4, with less pre-travel before the wall. Buy the G21 if you want maximum .45 ACP capacity in a proven platform with factory optic support. Skip it if you prefer a DA/SA action or want a gun under 27 oz for carry.
Best For
Strengths & Limitations
- 13+1 capacity is the highest of any .45 ACP handgun here, matching what many 9mm compacts hold
- Factory MOS optic cut eliminates the need for aftermarket slide work to mount a red dot
- At 29.1 oz with a polymer frame, it weighs 12.5 oz less than a steel-framed Sig 1911 Nitron while carrying 5 more rounds
- The 5.5 lb striker trigger has soft pre-travel that reviewers consistently describe as mushy compared to the HK HK45's 4.5 lb SA pull
- The polymer frame flexes slightly under .45 ACP recoil, and the lighter weight means more felt snap than steel-framed alternatives at 38-42 oz
Category Rankings
How the Glock G21 Gen5 MOS .45 ACP ranks among full-size .45 ACP handguns.
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Frequently Asked Questions
Can I use Glock 21 Gen4 magazines in the Gen5 MOS?
Yes. All Glock 21 magazines are compatible across generations. The Gen5's ambidextrous mag release may cause older Gen3 magazines to not drop free as cleanly, but Gen4 magazines work without issues. The 13-round factory magazine is the standard; no extended options exist from Glock.
What is the break-in period for the G21 Gen5 MOS?
Glock recommends no formal break-in period. Most owners report the gun runs reliably from the first magazine. The trigger does smooth out after the first 200-300 rounds as the connector surfaces polish, and the slide action loosens slightly from factory tightness.