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Building a 9mm AR is one of the more rewarding projects out there, and the bolt is where it all comes together. The Stern Defense SD BU9 handles that job with a complete assembly machined from 8620 AISI steel and finished in mag-phosphate for solid wear resistance under the heat and grime that comes with running pistol-caliber rounds. This is the same Glock-cut bolt Stern uses in their own factory 9mm uppers, so you know it's proven in real builds rather than just spec sheets.
The standout piece here is the custom 4140 billet extractor, which is a big deal for consistent extraction and ejection in a blowback 9mm platform. It fits into both Mil-Spec and Glock-pattern upper receivers and feeds from Glock magazines as well as Colt SMG mags, giving you flexibility depending on which lower and mag adapter you're running. Standard AR-15/M16 charging handles work with it, so there's nothing exotic to source when you're piecing a build together.
Stern designed this bolt around single-stage triggers with short resets, and it plays nicely with popular upgrades like the JP silent capture spring, the Law Tactical folding stock, and the Echo trigger. That makes it a smart pick whether you're chasing a lightweight PCC for the range or a folding-stock setup for compact storage. Builders who've fought with cheaper bolts that won't let a Colt-style mag fully seat tend to find the fit here just works the way it's supposed to.
Every bolt ships fully assembled with the firing pin, firing pin spring and retaining pin, extractor, and extractor spring already installed, along with the proprietary center pin and roll pins. Made in the U.S.A., it's a straightforward, dependable core for a dedicated 9mm upper or a pistol-caliber conversion you can count on trip after trip to the range.
This bolt is cut to run both Glock-pattern 9mm magazines and Colt SMG magazines, so it covers the two most common mag setups in the AR-9 world. Which one you use comes down to the lower or magazine adapter in your build. That flexibility is a big reason folks reach for this bolt when starting a dedicated 9mm project.
Yes, the SD BU9 drops into both Mil-Spec and Glock-pattern AR-15/M16 upper receivers. It also works with standard AR-15/M16 charging handles, so there's no need to hunt down anything special. That makes it a simple swap for completing or refreshing a 9mm upper.
It does. The bolt arrives complete with the firing pin, firing pin spring, retaining pin, extractor, extractor spring, and the proprietary center and roll pins already installed. You can drop it into your carrier and upper without sourcing extra small parts.
Stern designed this bolt around single-stage triggers with short resets, and it's compatible with the Echo trigger, the JP silent capture spring, and the Law Tactical folding stock. That makes it a strong foundation if you're planning a more tuned PCC or a folding-stock configuration. The custom 4140 billet extractor also helps keep ejection consistent through those setups.
| UPC | 860141001522 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | 004SDBU9D1M |
| Color | AR-15 9MM BOLT |
| Length | 7.7000 |
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