Smith & Wesson M&P Magwell Compatible Magazine Extension by Henning

Name: Smith & Wesson M&P Magwell Compatible Magazine Extension by Henning
Brand: Henning
SKU: H140-MS
Availability: InStock
Rating: 5 (2 reviews)

The Henning Group Magazine Extension Kit for Smith & Wesson M&P 9mm increases magazine capacity from 17 to 23 rounds! The design of our extension is a true extension of the internal shape of the factory magazine tube. Combined with a stainless steel, 13-coil magazine spring it is a proven and reliable solution. Our Smith & Wesson M&P 9mm magazine extension is CNC machined from 6061-T6 billet aluminum. This extension fits the USPSA 141.25mm gauge, and is legal for Carry optics, Limited Optics, Limited & Open divisions in USPSA.

Our latest design includes numbering dots, serrations for light side grab and a reinforced wall thickness.

We have three options for springs:

A. Henning Group spring (using factory follower). Installed on a 17 round mag, our spring ensures proper function.

B. MBX Follower and Spring increases capacity from 17 to 24 + 1. No Lock Back! Only for 17 round mags.

C. CSRG Competition Follower and Spring increases capacity from 17 to 24 + 1. No Lock Back! Only for 17 round mags.

Works with all magwells we have tried, including the SPEC SERIES V M&P 9 METAL HD

MBX Aftermarket Follower Kits does NOT LOCK slide back on empty.

MBX "Ultra Max" Spring & Follower

*Note This Product will not lock slide back on last round fired

ATTENTION!
Before Inserting Magazine Into Firearm

New MBX competition follower & spring sets need to be loaded 4-6 times to capacity preventing follower popping out when new , insuring spring set and the follower sits down in tube when new, this avoids any slide contact and damange to spring and follower voiding warranty as the competition follower is NOT held down by the slide stop and has minimal surface area , the competition follower is designed once spring is set to sit 1/4-3/8 below top of feed lips thus avoiding damaging slide contact with follower once magazine is empty.

Our Magazine Parts Policies

2 Reviews

5
Pad and stock internals

Posted by David Simpson on Aug 28th 2025

Love these baseplates. Quick to clean if needed. 23 rnd with factory spring and follower (for me), Will be replacing all my baseplates with these.
5
Best extension IMO

Posted by Jordan on May 13th 2025

I've been running these for a while now, and they are by far my favorite. Super easy to put on and take off for cleaning during matches. With the CSRG spring and follower, I can get 25 rounds reloadable.