Warne Magazine Extension — Black, +3 (9mm Luger) / +4 (.40 S&W), Fits S&W M&P 9/40 (3306 • UPC 656813108084)
Add capacity. Keep reliability. The Warne Magazine Extension for Smith & Wesson M&P 9/40 boosts your factory mag to +3 rounds in 9mm or +4 rounds in .40 S&W without compromising confidence on the range or during duty and competition. Built from durable, precision-machined material with a matte black finish, this low-profile base pad locks up tight, resists hard use, and maintains consistent feeding with the right spring setup.
Why Shooters Choose the Warne +3/+4 Extension
More rounds, same footprint: Gain +3 (9mm) or +4 (.40 S&W) capacity while preserving a compact, carryable profile that still fits most mag pouches.
Purpose-built for M&P 9/40: Designed to fit S&W M&P 9 and M&P 40 magazine bodies (select full-size/compact mags—see compatibility notes).
Reliable lock-up: Positive retention system helps prevent walk-off under recoil, drops, and high-round-count training.
Fast reloads: Extended base pad improves purchase during mag changes—especially with gloves or in wet conditions.
Durable construction: Engineered to handle duty use, USPSA/IDPA training, and everyday range abuse.
Clean, black finish: Low-glare black exterior blends with factory aesthetics for a professional, OEM-like look.
Key Features at a Glance
Model: 3306
Finish/Color: Black
Capacity Increase: +3 rounds (9mm Luger) • +4 rounds (.40 S&W)
Fitment: S&W M&P 9/40 (magazine-dependent; see notes)
Use Case: Competition • Training • Range • Duty/EDC (where legal)
UPC: 656813108084
Performance Benefits You’ll Notice
Quicker indexing: The slightly extended base gives your hand a consistent reference point out of the pouch or pocket.
Improved balance: Added base weight promotes confident seating on closed slides and consistent drops during reloads.
Field-serviceable: Simple on/off design supports fast cleaning and spring swaps.
Pro Tip: Always verify your magazine spring is appropriate for an extended base (many shooters upgrade to a stronger spring for optimal feeding and slide lock).
Compatibility & Fit Notes
Designed for Smith & Wesson M&P 9 and M&P 40 double-stack magazines.
Capacity claims: +3 (9mm Luger), +4 (.40 S&W), assuming standard-length magazines in good condition with compatible follower/spring.
May not fit Shield/Shield EZ/Single-stack models or certain compact/10-round restricted magazines.
Check your mag’s baseplate style, body windowing, and locking plate before installation.
Installation Overview
Unload & clear the firearm and workspace.
Depress the locking plate button and remove the factory floorplate carefully (springs are under tension).
Inspect the follower & spring; replace with a heavy-duty spring if recommended.
Slide on the Warne extension until it locks positively.
Function-check: Manually cycle rounds (dummy rounds preferred), verify feeding, slide lock, and drop-free operation.
Range-validate with your carry/competition ammo.
Always follow manufacturer instructions. If unsure, consult a qualified armorer.
Specs
Brand: Warne
Product Type: Magazine base pad/extension
Color: Black
Added Capacity: +3 (9mm), +4 (.40 S&W)
Firearm Platform: S&W M&P 9/40 (magazine dependent)
Model Number: 3306
UPC: 656813108084
Compliance & Best Practices
Know your laws: Magazine capacity limits vary by jurisdiction. Confirm legality for your area and intended use.
Competition rules: Some divisions restrict overall mag length or capacity. Check your USPSA/IDPA rulebook before match day.
Maintenance: Periodically inspect the retention screw/pin (if present) and spring condition; replace worn parts promptly.
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FAQ
Q: Will this work with my M&P Shield or Shield Plus?
A: No. This extension is designed for M&P 9/40 double-stack mags, not Shield/Shield Plus single-stack magazines.
Q: Do I need a new spring?
A: Many users run a stronger magazine spring for best reliability with added capacity. Follow Warne’s guidance or use a reputable spring upgrade.
Q: Will it fit 10-round restricted magazines?
A: Often not. Extensions may be incompatible with reduced-capacity bodies and may be illegal in some locations. Verify before purchase.
Q: Is the finish durable?
A: Yes—the black, low-glare finish is designed to resist sweat, solvent, and everyday range wear.
Q: Can I install it myself?
A: Yes, with basic tools and care. If you’re unfamiliar with mag disassembly, a gunsmith or armorer can install it quickly.
Upgrade your S&W M&P 9/40 with the Warne Magazine Extension (3306) and get the extra rounds, faster reloads, and confident handling you want—without sacrificing reliability or style.
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