You press the trigger once and the Glock fires twice. Sometimes it's a fast "burp" of two rounds; sometimes the gun fires as you let the trigger out. This is called doubling (or hammer/striker follow), and on a Glock it almost always traces back to the fire-control geometry — most often a connector with the wrong angle or a trigger bar that isn't resetting. It is a malfunction, not a feature, and it needs to be corrected before the pistol is used again. Here's what's happening and how to chase it down.
A pistol that doubles is firing without command and is unsafe to shoot. Stop immediately, keep it pointed in a safe direction, drop the magazine, clear the chamber, and bench it. Do all inspection with the pistol unloaded and no ammunition nearby. If you're not comfortable working inside the fire-control group, take it to a qualified gunsmith.
What "Doubling" Actually Is
A Glock is striker-fired. Each shot, the trigger bar pulls the striker back and then the connector cams the trigger bar downward, releasing the striker to fire. For the next shot to be controlled, the trigger bar has to spring back up and re-capture the striker as the slide cycles. That reset is the whole game.
Doubling happens when the trigger bar fails to reset and re-capture the striker. Instead of being held, the striker follows the slide forward and fires a second round on its own. So while it can feel like a "trigger" problem, it's really a reset problem — and the connector is the part that most directly governs that timing.
(Worth noting: this is different from a true slam fire, where a free or fouled firing pin sets a round off as the action closes. Doubling is a fire-control reset issue, not a firing-pin issue.)
First, rule out the shooter. A fast pair from riding the reset, a heavy trigger-finger "bump" under recoil, or sympathetic muscle response can feel like a double but isn't a defect. True doubling — the one this guide is about — is the gun firing a second round with your finger held still. If the pistol fires on its own with your finger stationary or as the trigger resets, treat it as a mechanical fault and stop shooting.
Why the Connector Angle Matters
The connector is the small angled leaf in the trigger mechanism housing. Its angle does two jobs at once: it sets trigger pull weight, and it controls exactly how far and how long the trigger bar is cammed down. If that geometry is off — too aggressive, reshaped, worn, or just the wrong part — the trigger bar can be held down too long or not return cleanly, and it never re-engages the striker. The result is a double.
This is why doubling so often appears right after a trigger job: an aftermarket connector, a hand-polished connector, or a polished trigger bar changes that engagement surface. Connector geometry is precision work measured in thousandths — it is not a bench project, and "smoothing" it by hand is a common way to create exactly this malfunction.
Common Causes
| Cause | What's happening |
|---|---|
| Wrong or altered connector angle | Trigger bar is cammed down too far or won't return, so the striker is never re-captured |
| Hand-polished connector or trigger bar | Material removed from the engagement surface changes reset geometry |
| Worn or damaged connector | The reset face rounds over and no longer lets the bar return crisply |
| Wrong-generation or mismatched part | A connector or trigger bar not matched to the frame/housing seats at the wrong angle |
| Improper reassembly | Connector not fully seated in the trigger mechanism housing, or a tired trigger spring |
How to Troubleshoot and Resolve It
Pistol unloaded, ammunition off the bench, in this order:
- Stop using it. A doubling pistol is unsafe. Don't try to reproduce it with live rounds to "confirm."
- Find out what changed. Did this start after a trigger kit, a connector swap, or a polish job? That's almost always the answer. Note every aftermarket part in the fire-control group.
- Return to a known-good baseline. The most reliable fix is to reinstall a correct, factory-spec connector and trigger bar matched to your generation, fully seated in the trigger mechanism housing. If an aftermarket or hand-worked connector is in there, that's the first thing to pull.
- Inspect the engagement surfaces. Look at the connector's reset face and the trigger bar cruciform for rounding, gouges, or polishing. Damaged parts get replaced, not re-shaped.
- Confirm the part matches the pistol. Verify the connector and trigger bar are correct for your model and generation — a mismatched part can seat at the wrong angle.
- If it still doubles on factory-spec parts, stop and see a gunsmith. Fire-control geometry that misbehaves with correct parts needs hands-on diagnosis. This is not a "shoot it and see" situation.
Preventing It
- Use quality, correctly-spec'd fire-control parts and install them properly — or have them installed.
- Don't hand-polish or reshape the connector or trigger bar engagement surfaces.
- Keep a set of factory-spec parts as your baseline so you can always return to a known-good configuration.
- If a pistol ever doubles, retire it from use until it's diagnosed and fixed.
Parts to Get Back to Known-Good
Most doubling fixes come down to putting correct, properly-fitted fire-control parts back in:
- An OEM trigger mechanism housing with ejector for Glock Gen 1–3 restores a factory-spec seat for the connector.
- A complete Glock 19/23 lower parts kit rebuilds the whole fire-control group as a matched set.
- Prefer a lighter pull done right? A quality drop-in trigger connector made to spec is the safe way — not a hand-filed one.
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